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Wednesday, June 8, 2011

Finding Noah, then and now: Part 2—"When and where did Noah sail his ark?"

Introduction

Thus far, I have reiterated how the flood narrative of Genesis 6–9 was used exegetically as a type for creation and judgment, and more specifically for God's redemption through Christ. The story fits canonically within the broader context of the Torah, linking God's work in the Exodus with that from antiquity. Because of its mirrored relationship to the creation narrative (Gen. 1–3), the story of Noah also provides an appropriate analog for God's imminent and future judgment throughout the Bible, as well as His means of salvation.

Few Christians would disagree, I think, on these basic points. More spirited debate has focused rather on the narrative's place in history, including its relationship to the facts of geology. Young (1995) chronicled how the church's perception of the flood has changed repeatedly in light of new evidence from science—from Aristotle to Steno to Hutton to modern geology. Universal agreement on the historical and scientific implications of the Genesis narrative has never existed in the life of the church, and today is no exception. In addition, numerous expeditions have produced more fanciful stories than remnants of the ark. Did the ark ever exist, or have we simply been looking in the wrong place?

Quests for the ark—today, in history, and in geology—are intimately linked to our understanding of the text. Those convinced of a global flood in the text will search for evidence in rocks around the world. Conversely, those convinced of only local floods in the rocks will search for supporting evidence in the text. Reconciling both records is not easy, and I admit my own bias in the process. But this bias is universal and unavoidable, even to critics of the biblical narrative. One can not presume to have a final answer without demonstrating how the same conclusion may be drawn independently from all disciplines. Thus I hope you will give me credit here, if nothing else, for trying to be consistent.

As a geologist, I recognize that there is no evidence of a global flood in Earth history. Neither is there evidence of a global interruption to human civilization in the last 10,000 years. Thus I have used this blog to highlight the shortcomings of Flood geology, and demonstrate where its hypotheses have been thoroughly falsified. I have done this primarily to call others to academic (and Christian) honesty, and so I welcome the same feedback. For those interested in further reading—or yet unconvinced by my own analysis—I highly recommend The Bible, Rocks and Time by Young and Stearley (2004; or start with a helpful review of the book here).

Though you may not share my conclusions about the geological and archaeological evidence against a global flood, I will assume them here as being well established and encourage you to pursue that issue further. My goal here is to examine 1) whether the biblical text requires a 'global-flood' interpretation; and 2) whether the flood narrative may be identified in history, archaeology, and geology. By way of preface, I generally agree with Dr. Carol Hill's conclusions about Noah in history (2001; article found here) and her comments on the text (2002; article found here).

I also cite two other papers by Carol and her husband (Hill, C.A. 2006; Hill, A.E., 2006) that examined the hydrology of a catastrophic flood in Mesopotamia. I came across their work after I began to write Part 2 of this series, and was thoroughly impressed. The articles are well thought out, and deserve the attention of anyone seriously interested in the historical question of Noah. I will reiterate some of their arguments below, adding my own thoughts between, but I should admit up front that I can offer little more, academically, than they have produced.

Israel retells the story of Noah: polemical historiography in the heart of Canaan

Stories about the past are told to comment on the present, in an effort to better write the future. In this sense, historiography in general—and biblical narrative in particular—is not merely an intellectual quest, but often pastoral and even eschatological. By reminding us where we've been or whence we came, stories tell us where we ought to be and how to get there. That doesn't mean we can't discern the historical referents, but it does make the quest more challenging.

Contrary to subconscious perception, the story of Noah was written for an audience far removed from our own culture. The author of Genesis took a well known history and recast it as an apologetic for the covenant God of Israel, over against those of the surrounding nations (Enns, 2005). Everyone knew the story of the flood, but Israel's neighbors had long credited pagan gods with the events. The flood narrative in Genesis thus served in part to tell Israel that God had been at work since the beginning—long before Moses or even Abrahaam. Moreover, He acted then for Noah just as he had acted for them in Egypt. The covenant God of Israel would not tolerate wickedness, violence, and idolatry among His covenant people. But at the same time, He would act on behalf of those faithful to Him, providing both the means of atonement and deliverance for His people—then in the form of an ark; now in the tabernacle.

The tale of Noah is not just history, it is historiography. These events are retold with specific motives; the author has an agenda. When the story is placed canonically within the Pentateuch, we find how the author has made his case that YHWH, the covenant God of Israel, deserves worship and praise, unlike the pagan gods of the nations who only bicker with each other to fulfill greedy passions and lusts (e.g. compare Gen. 1–11 with contemporary creation/flood epics; cf. Walton, 2007). The story of Noah and his ark is thus polemic through and through. Moreover, it was structured to comment directly on the current state of Israel, specifically with regard to their customs and laws, and provide hope to the vulnerable Israelites. They were surrounded by greed, hostility, and pagan worship, and were but an unfaithful generation away from bringing judgment upon themselves. I will return to this point when I discuss the post-Flood covenants.

Form criticism and the flood narrative

The flood story in Genesis does comprise an historical account, but much of the account elucidates the theological reasons behind the catastrophe (i.e. How was God involved and why did He do this?). Another challenge comes in the style of the narrative, which was not written like an article out of Science. The form is rather semi-poetic (Kline, 1958), and fits nicely into that of ancient Hebrew storytelling, where parallelism abounds (i.e. the same thing is said twice, in two different forms). Genesis 7:17–23 is a great example of this.

As an aside, I am not saying that the literary form of Genesis 6–9 implies it was written only metaphorically, abstractly, or somehow removed from real events in history. I don't think the narrative would make sense unless the events were real and people knew about them. Consider a personal example from my own history:

My aunt died after a 6-year battle with breast cancer on Sept. 9, 2001. The rest of my family left immediately for Colorado, but I was stuck in Utah because I was enrolled in 5 classes and couldn't afford a whole week away from school. My uncle bought a plane ticket from Seattle to come down a couple days before the funeral—scheduled on Sept. 13th—but I couldn't afford a last-minute flight. I was disheartened that I would miss the funeral of my only aunt, but as it turned out, I did make it to the funeral. As you can imagine, my uncle was not allowed to make his flight on Sept. 11th, so he rented a car and drove down. Since Utah was on the way, he picked me up and we both made it in time for the viewing and the funeral.

If I were a great storyteller or poet, I could recast these events in a form not unlike the Genesis narrative. A careful reader, even hundreds of years from now, could then use my story to rebuild the timeline of national events that week in September. It will contain historical facts and details—accurate ones at that. But since the primary goal of my story would be to relay how the providence of God allowed me closure in my aunt's death, the account cannot simply be read at 'face value' if one were interested only in historical details. Discerning those details requires some work on the part of the reader.

Who is the audience of Genesis 6–9?

Knowing the original audience is vital in literary criticism. There remain a few difficulties, however, in determining the original audience of the flood narrative, not least in the challenges of modern biblical scholarship. The prevailing hypothesis is that Genesis was written in parts between the division of the kingdom (after David, ~1,000 B.C.) and the Babylonian conquest (586 B.C.), and later redacted during or after the return from exile (538 B.C.) along with the rest of the Pentateuch and Deuteronomic history. This is known as the Documentary Hypothesis, and I recommend Who Wrote the Bible? by Friedman (1997) for a scholarly introduction to how this idea has evolved over the past few centuries.

Since the oldest physical copy of the Tanakh is found in the Dead Sea Scrolls (ca. 100 B.C.), theories about the authorship and date of Genesis must rely almost entirely on internal evidence. Thus the Documentary Hypothesis has changed, and will continue to change as more evidence comes to light. Most conservative evangelicals have rejected the Documentary Hypothesis outright, opting instead for a Mosaic authorship (based Talmudic tradition and New Testament references to Moses). I am not qualified to draw a final conclusion either way, but I do feel that opponents of the hypothesis have yet to answer satisfactorily many of the textual challenges raised (e.g. duplicate accounts with unique vocabularies; interrupted chronologies; references to people, places, and events long after Moses's death), and that some of their efforts are misguided.

For example, the Documentary Hypothesis does not reject that Moses gave a written law to Israel (called Torah), but only that Moses, or any single author, wrote the entire Pentateuch in the form we have today. Even the most conservative evangelicals recognize that a later author must have written some parts of the Pentateuch (e.g. the account of Moses's death), and many are comfortable saying that Moses did not author any of Genesis, minus a few edits (e.g. article here by Russell Griggs; see also Morris, 1976).

On the other hand, the initial proponents of the Documentary Hypothesis assumed too little about the literary abilities of the ancient Near East, and too much about the evolution of religions. Ancient Mesopotamia was not characterized by a primitive society, practicing some simplified form of a fertility religion, passed on through oral tradition alone. Thousands of clay tablets, recovered in the past two centuries, reveal that ancient Sumeria was rather a highly ordered civilization, replete with priests, temples, and law codes—as early as the fourth millenium B.C. (Walton, 2007)! They were not only literate, but skillfully so. The same has been demonstrated for Israel, at least as far back as the 11th century B.C. Consequently, proposed dates of authorship for much of the Pentateuch have been pushed back several times, and Friedman (1997) suggests that all of J, E, and P were written long before the destruction of the first temple.

There is no reason to doubt a priori that written records could have been passed on from Abrahaam to Moses to the post-Exilic scribes. The question is whether and how they have been rewritten since that time (and they would have had to, if only to account for the evolving language of the people). The contextual antiquity of Genesis 1–11 is obvious, even if the form is more recent. Moreover, the accounts were not simply fabricated from Babylonian records, despite the minor similarities. Details about the geography, politics, and economics of the region suggest that the original author was personally familiar with ancient Sumeria, in addition to her famous epics (Gilgamesh, Atrahasis, etc.). Use of ancient words and numbering systems further attest to this fact (Hill, 2001).

Whether or not the Pentateuch was compiled by Ezra during the Babylonian exile (Friedman, 1997), the story of Noah would have been told—even written down—in some form long before Moses. Perhaps a Mosaic composition inspired the words we now attribute to J (and thus P)? Whatever the case, I think we can say with confidence that Genesis 6–9 was written in the form we have today sometime after the Exodus, but certainly before the first temple was destroyed (as proposed by Friedman, 1997), because it fits both chronologically and canonically into the Torah as a whole, but retains details from antiquity (Sumeria). If so, we should be conscious of its relationship to the rest of the Torah when interpreting the historical particulars, and try to read it from the perspective of an Israelite that just settled in a recently conquered Canaan.

Flood narrative(s)?

Though I do not offer my full, unequivocal support to the Documentary Hypothesis, I am convinced that Genesis 6–9 does contain two flood narratives (call them J and P for convenience). Several parts of the story are told twice in different ways. For example, 6:9–13 (P) is essentially a repeat of 6:1–8 (J). The beginning of chapter 8 (J) repeats the end of chapter 7 (P) in terms of gathering the animals. Everyone enters the ark in 7:6–9 (J), and again in 7:13–16 (P). Lastly, the covenant in chapter 9 (P) repeats that given at the end of chapter 8 (J), but with added detail.

Whenever the narrative contains a duplicate account, there are key differences. Most notable is the name of God used (Elohim vs. YHWH), which has long been noted by Christian scholars. The end of chapter 6 says to gather 2 of every kind of animal, including birds, but the beginning of chapter 7 says to gather 7 of every clean animal, and 7 of every kind of bird. Part of the narrative seems to indicate the flood would last (or did last) only 40 days, but the rest outlines a year-long deluge. In both forms of the covenant, God promises not to wipe out the life of the land on account of man's sin, but the account in Chapter 9 gives commentary on the law and priestly duties, whereas the Chapter 8 account simply reverses the curses of Genesis 3 and promises not to interfere again with the natural order given there.

These apparent contradictions can be resolved without assuming two flood narratives (i.e. as the text stands), but the task is done more easily if understood this way. For Noah to eat meat after the flood (Gen. 9:3), for example, the animals would have to be sacrificed. [Note: Animal sacrifice was not just a ceremonial cremation to appease God's wrath, but the only means by which animals were consumed. Only clean animals were fit for eating, because only clean animals were fit for sacrifice. Thus eating meat in the early church sometimes required eating animals sacrificed to idols (1 Cor. 8; Rom. 14)] Since the P account does not include Noah's offering after the flood (8:20), the extra animals are not mentioned at the end of chapter 6 (or they are included, subtextually, in the "food for you" of 6:21). On the other hand, the seven pairs of 7:2–3 set up the narrative for an offering in 8:20–21. These differences are not contradictions, therefore, but follow the respective purviews of the individual authors (at least one of whom may have indeed been Moses or Aaron).

Many still deny that the flood narrative was redacted from two accounts, but I don't see any good reason. The flow of the text is interrupted in several places (e.g. 7:11), and it's hard to say why a single original author would switch between two different names for God, seemingly arbitrarily. Different vocabularies are used where the story repeats itself: 'male and female' vs. 'a male and his female'; 'expired' vs. 'died'; 'raven' vs. 'dove'. Moreover, the timeline of the flood (see below) loses much of its significance within this interpretation. I believe that the more parsimonious conclusion is that a single author, inspired by God, redacted the two accounts to fully explain Israel's place in history (i.e. in light of the flood) as the covenant people of God. Whatever the case, the literary structure of Genesis 6–9 is an amazing work of art (see Wenham, 1994 for detailed analysis). Each account is equally poetic and well structured when considered individually. Personally, I think this only adds to the magnificence of the narrative as we know it, as well its ultimate Author.


What does the account of Genesis 6–9 actually tell us?

The literal reading of Genesis 6–9

We are now to the point where the rubber meets the road. So far, I have tried to establish that 1) the flood narrative of Genesis was passed down from antiquity, but rewritten for post-Exodus Israel; 2) the account was written partly as an apologetic for the covenant God of Israel, elucidating also the place of His covenant people in history; 3) the literary genre of Genesis 6–9 is epic or myth, in that it uses familiar history to unfold the worldview of the authors; thus 4) we must properly apply form criticism to uncover the historical and scientific particulars; but 5) we must be careful not to impose our own cosmology and worldview on the text, as many earlier commentators have done. In light of these principles, we can outline the literal reading of Genesis 6–9 and compare it against history, archaeology, and geology.

Homeland of Noah

We are not given an explicit geographic location for Noah, but we do have some details about where he ends up. After the flood, he begins farming and plants a vineyard. Before this, a dove returns to the ark with an olive branch. Unless Noah's family travelled a long way before settling down (this must be read into the text), we can assume that he ended up in a favorable spot for growing olives and grapes (temperate climate with sufficient rainfall and elevation).

The garden of Eden is described in the context of 4 rivers known to ancient Sumeria. Abrahaam came from Ur, close to where the same rivers flowed. Is there any reason from the text to think Noah originally lived outside of the Mesopotamian valley we know? Morris (1976), and others after him, suggested that Noah's family named rivers in the new world after those in the pre-Flood world. Unless one decides a priori that the flood was global and reshaped the whole planet, however, there is no reason for this rationalization. In fact, it forces a rather awkward feel on the text. The geographic continuity from Eden to Abrahaam stands as textual evidence against the foundation of Flood geology, and a literal reading of the text places Noah in Mesopotamia before the flood.

The literary proximity of the Genesis narrative to Sumerian records corroborates the notion that Noah's tale descended from that region. In the Epic of Gilgamesh, the head survivor of the ark was 'king' of a city called Shuruppak, located north of Ur in the central Mesopotamian valley. Hill (2001) argues that the biblical chronology also places Noah at the end of the Jemdet Nasr period (~2900 B.C.), when the Gilgamesh protagonist was said to reign. Furthermore, the 'overlying' 1st Dynasty period of Sumeria is separated stratigraphically at Shuruppak by a 5–11 feet-thick, water-lain silt deposit, which is possibly coeval with the earliest flood deposits at Kish, located at the north end of the valley (MacDonald, 1988), and even Uruk (Morozova, 2005; Hill, 2006). Kish was also known to later Sumerians as the first city rebuilt after the deluge (politically, that is; cf. Sumerian Kings List).

Universal language of the narrative

Whether in describing the extent of judgment, what kinds of animals were to board, or the extent of the flood waters, the Genesis narrative speaks of 'all the land', 'everything that has breath', or 'all the mountains under the high heavens'. All terrestrial life is destroyed, and the high hills were covered. I agree with the YEC reading on this point: the flood of Gen. 6–9 is a global/universal flood.

Noah's globe, however, was quite a bit smaller and flatter than our own. I would argue, therefore, that since the narrative is firmly rooted in the cosmology and geography of the ancient near East (e.g. reference to the floodgates of heaven and fountains of the deep—physical barriers that kept the waters above and the waters below from overcoming the dry land), we should not apply this language to our own picture of the planet. As mentioned in Part 1, the end goal of Gen. 6–9 was to return the land to a state of chaos (Gen. 1:2) through uncreation, and reestablish God's covenant people through Noah—a new Adam. God brought life to the land of ancient Mesopotamia, placed Adam there, and then made a covenant with Adam and Eve. Through the flood, He judged those that abandoned the covenant and destroyed the fruitful land they had enjoyed. From Noah's perspective, the whole land given by God was indeed overcome with water and all life perished, save those aboard the ark.

Ancient Israel did not have a word for "planet Earth" (Hill, 2002), and they rather used a word (translated earth) that referred to the land occupied by their people. The same descriptors are used for the judgment against Sodom and Gomorroah, Egypt, Israel at the hands of Assyria/Babylon, or even Jerusalem in the NT. If we want to interpret "the waters covered all the land" as "all of planet Earth was submerged", then we should also interpret the famine of Joseph's time (Gen. 41) to apply to all of Africa, Asia, Europe, and even America. Consistency is key.

Universal language is also necessary to communicate the theological message of God's judgment and redemption. I concur with Matthew Henry that the hills are mentioned partly because the hills were always thought of as a place of refuge (e.g. Jer. 49:14–16). Matthew 24 is a good example from the New Testament, in a similar context. But God's judgment is inescapable—there is nowhere to run.

Added confusion comes with the definition of the word translated 'mountain' or 'hill'. It could mean the highlands, as opposed to the valley. It could also mean mountain peaks. But it could also mean the city mounds and ziggurats of ancient Sumeria! The same word refers to all (Hill, 2002). But if the author is first concerned with the extent of God's judgment, rather than paleobathymetry or hydrology (a good assumption, in my opinion), then the exact rendering of the word is not relevant. All three will work, as long as it is understood that everything in sight was somehow covered by water. I will return to this point when discussing the depth/extent of the flood.

On a side note, I believe the YEC interpretation yields some inconsistency in their understanding of the universality of the flood. The narrative says that every kind of terrestrial/avian animal was preserved on the ark, but that everything outside, in which there was the breath of life, died. Numerous YECs (e.g. Woodmorappe, 1996) have debated how all the animals could fit, let alone live on the ark. But in each case, the author must allow that not every family/genus/species of terrestrial and avian life was on the ark. We know today that there would not be room for these creatures, unless some super-evolutionary and migratory event occurred after the flood (and by super, I mean unrealistic and impossible). Thus Woodmorappe (1996) and others have cited how various birds, amphibians, etc. could have survived the flood waters outside of the ark. The inconsistency here is obvious, in my opinion. Either all species of terrestrial and avian life today are descended from ark survivors, or the flood was not global in a modern sense of the word.

Construction of the ark

Very specific measurements are given for the size of the ark, as well as its composition. I don't really have any comments on the composition of the ark, except that the type of wood was foreign to those used in later construction (the word is never used again in the OT). If nothing else, this could suggest that the ark was built in a land other than Canaan, where different kinds of trees were growing, or that the word was passed down from antiquity. I see no immediate reason not to take the physical dimensions of the ark at face value, though I would be very interested to see someone build a full size model that could survive on open water, rather than on dry land! Hill (2002) suggests that the original dimensions could have been disguised in the fact that the Sumerians used a different numbering system (sexagesimal) than the Hebrews. Physical proportions of the ark would allow for maximum stability, but using the Sumerian cubit (72 cm), the dimensions are about 6 times that of large, Mesopotamian river boats.

Some have related the dimensions of the ark directly to the tabernacle (dimensions given in Exodus 27), providing an intertextual link (i.e. they did serve a similar purpose). The height of the ark (30 cubits), for example, is exactly 3 times the height of the tabernacle (10 cubits), and the surface area (300 x 50 = 15,000 cubits) is exactly 3 times that of the courtyard (50 x 100 = 5,000 cubits). In addition, Moses himself was carried by an ark (same word) to safety as an infant. These textual links allow the ark narrative to be read partly as a commentary on God's redemptive plan, particularly in the meaning of the tabernacle. Thus the actual dimensions of the original ark are less important, compared to the point that the ark is a type for the tabernacle (and ultimately, Christ's church), and may have been rewritten (or rounded off) to drive that point.

Disputes on how to interpret the blueprint are perhaps trivial (e.g. how the 'window' looked, whether the bow was rounded, etc.), but the command to coat the ark with pitch corroborates a limited flood, over against a Flood geology interpretation. The primary meaning of the word would suggest that bitumen from oil seeps was used (which should not have existed in a Flood geology scenario). Contemporary uses of the word in ancient literature, as well as later uses in the Bible, also confirm this interpretation. YEC commentators hypothesized the use of harvested tree resin (e.g. here), but I think their arguments are very poor. First, why would the author use a term specifically used for oil in a land where oil seeps abound? The product of harvested tree resin may be called pitch, just like our English translation of Genesis, but it has nothing in common with the Hebrew word. Second, the assumption that Noah had the technology to harvest tree resin is entirely arbitrary and imposes on the plain reading of the text. Lastly, harvesting tree resin is a very slow, time consuming process that is counterproductive to harvesting wood for a giant boat (cf. RTB article here). A much simpler, straightforward reading of the text is that Noah did live in ancient Sumeria, and used bitumen from oil seeps like any other ship builder of his time.

The Sumerians regularly imported pitch and cedar from upriver (Hill, 2002; Morozova, 2005), and the former was also used to build the Tower of Babel (Gen. 11), ziggurats, and earlier temple mounds. A literal reading suggests the source of the pitch was petroleum based, contrary to the Flood geology hypothesis that oil is a geological product of the flood. Flood geologists cannot account for the geological production of oil in a recent flood scenario, however, so the weight of archaeology, geology, and the biblical text falls in favor of a 'local flood' reading (more about oil here).

Depth and extent of the flood

In short, I don't think the language of Genesis (7 in particular) requires us to think that the flood was any more than 30–50 ft (depth of a catastrophic, but localized flood on the Mesopotamian valley). When the text says "the mountains were covered", it cannot be referring to any of the high ranges we know today (including Mt. Ararat), because the original (Sumerian) audience of the flood narrative, as well as the participants, did not know any mountains outside of those north of Sumeria (northern Iraq/southern Turkey today). Back in Noah's and Abraham's day, these were called the mountains of Urartu (rrt, rendered Ararat). Logical conclusion? The hills that were covered were located in Mesopotamia, and the resting place of the ark was northern Iraq or southern Turkey.

What are the hills that were covered by the deluge? One possibility is that the waters were just high enough to cover the hills immediately surrounding the alluvial plains of Mesopotamia (e.g. Urartu), but I think that given the topography of the region (these mountains are hundreds to thousands of feet high), a flood this deep is out of the question. Moreover, if such a flood did occur, there would be obvious evidence that could be correlated across adjacent continents. In other words, this option faces the same problem as conventional Flood geology: there is no such evidence.

If the language of Genesis 8 were meant to be phenomenological (as in the creation psalms), however, the interpretation might be recovered. Picture yourself on the floodplains of northern Mesopotamia (Google Earth is a great tool for this). The hills are just visible on the horizon. But if enough rain fell that the entire valley flooded for days to weeks/months, even the highest mountain peaks would not be visible to you any longer. One reason is that the horizon would be obscured with flood water. The other is that clouds would, quite literally, cover all the mountains (I lived along the Wasatch Front in Utah for 12 years and whenever it rained, the mountains were invisible from even a mile away). From any point of view, "all the mountains under the high heavens" would indeed be "covered". Moreover, the floodwaters would push everything out toward the edge of the floodplain (i.e. to the base of the hills). This interpretation explains the language used to describe the rising waters, as well as the resting place of the ark.

Although the Hebrew word for "covered" (as well as the Septuagint rendering) primarily refers to concealing something from view, the syntax demands that the rising waters (not falling) were responsible for the concealing. We should read Gen. 7:19–20, therefore, to mean that the "high hills" were indeed submerged by the floodwaters. I propose a simpler interpretation, taking into account the geography, hydrology, and architecture of ancient Sumeria, as well as the 'semi-poetic' style of the narrative—particularly that of J.

If Noah were originally a prominent figure of Shuruppak (Hill, 2001), then the only "hills" of the land would have been natural levees (3–4 meters; Morozova, 2005) and the mounds upon which the cities were built. In fact, these mounds were built specifically to avoid damage from flooding (Heyvaert and Baeteman, 2008). Hill (2002) speculates that since the Sumerian word for ziggurat was derived from mountain/hill (literally, 'temple mound'), it could be the referent of Gen. 7:19–20. The high Sumerian and Babylonian ziggurats (up to 300 ft), however, were not prominent in Mesopotamia until long after Noah's time. Instead, Sumerians of the 4th/3rd millennia B.C. built much smaller structures (1-2 stories) on natural and artificial mounds, which they simply called: mountains.

Most commentators have read Gen. 7:19–20 to mean that the waters covered the mountains, and then rose an additional 15 cubits. The two verses form a basic parallelism, however, rather than sequential events:

19: The water prevailed more and more upon the earth, so that all the high mountains everywhere under the heavens were covered.
20: The water prevailed fifteen cubits higher, and the mountains were covered.

The parallelism is more obvious in the natural, chiastic structure of the J narrative (see Appendix below), in which these two verses mark the climax—structurally and contextually—of the story. Thus the author of J writes that after the ark was afloat (7:18), it took 15 cubits to cover the hills (or "the water rose more than 15 cubits, and the mountains were covered", cf. NIV footnote). Using the Sumerian cubit (72 cm), this implies a depth of ~35 feet plus the draft of the ark. The mound at Shuruppak ranged from 3 to 9 meters above the floodplain (Martin, 1983), or a maximum of about 30 feet.

A 40-foot flood would have been sufficient to cover all hills and structures under Noah's sky. It is also consistent with the hydrology of the Mesopotamian floodplain (i.e. the gradient, width, and area of the drainage basin) in the case of a rare and extreme avulsion of the Tigris. Flood deposits at Shurrupak and Kish confirm that a large, lasting flood covered the cities at the time when Noah is said to have lived. As Morozova (2005) puts it: "In modern avulsion belts, several meters of silt and sand are deposited during long-term inundation...whereas typical floodplain deposition by annual floods, very common events in lower Mesopotamia, is only on the order of millimeters or centimeters."

The specificity of the 15 cubits in 7:20 should lead us to ask how the measurement was taken. As Hill (2002) rightly points out, the measurement is quite meaningless in a global flood scenario. But in the case of a ~40-ft. flood on the Sumerian plain, Noah or a person on the ark could have easily obtained the depth by conventional means.

Resting place of the ark

That Noah's ark came to rest in northern Iraq or sourthern Turkey is further corroborated by the fact that Noah's dove brought back an olive branch, and that he planted a vineyard shortly after. Grapes and olives can grow well in the 'hills of Urartu', but not in the lower Sumerian plain (or Mt. Ararat, for that matter). Consequently, Hill (2002) argues that the strength of the wine overwhelmed Noah because he may have been quite new to the drink (the national drink of Sumeria was a weaker, malted barley).

Contrary to long-standing tradition, Genesis 8 does not suggest that the ark came to rest high on a mountain. The resting place of the ark was "the mountains of Urartu", which could mean anything from the floodplains at the base of the hills (where people actually lived) to the mountain peaks of northern Iraq. The former is a political description: the land dominated by the 'Kingdom of Urartu' (e.g. Isa. 37:38). No details are given as to the elevation of the ark when it came to rest—only the geography. Hill (2002, p. 176) points out that the Urartian region only covered the "northern fringes of Mesopotamia" in the 3rd millenium B.C., expanding northward into modern-day Armenia more than a thousand years later. Combined with early historical accounts about the ark's resting place, she argues for Cizre, Turkey as the most likely candidate.

The scenario of Hill (2002) is not without difficulties. First, Genesis 8 says that the mountain tops became visible after the ark had come to rest. Secondly, one must explain how the ark traveled up gradient to the north (approximately from Shuruppak to Cizre), rather than out toward the Persian Gulf. In response to the second challenge, Hill (2006; husband of the former) constructed a physical model that accounted for the hydrology of a year-long, 40-ft. deep flood over Mesopotamia, as well as size and approximate weight of the ark. He concluded that a strong, prevalent wind from the Gulf (cf. Gen. 8:1) could provide the sufficient drag force needed to move the ark from point A (Shuruppak) to point B (Cizre) in less than 40 days.

Hill's model assumed the full dimensions of the ark (Gen. 6), a range of wood densities, and cubit lengths between 18–21.6 inches. In other words, the model complies with even the most rigid hermeneutic. Alternatively, I believe it is entirely possible that Noah's ark was much smaller—closer to that of a large Mesopotamian cargo ship (see above). Also, nearly every commentator has assumed that the ark's movement was entirely at the mercy of the wind and currents. But the Sumerians knew how to get up and down the rivers (even to Urartu). Although the text of the biblical narrative does not specifically mention any effort to move or steer the ship, we should not assume that is the case, particularly if the ark moved upstream! This assumption constitutes an argument from silence that goes against the prevailing archaeological evidence regarding Mesopotamian trade routes.

Lastly, the fact that the mountain tops become visible after the ark comes to rest may seem to require that the ark rested on top of a mountain peak, but only if the "hills of Urartu" is taken to mean a structure and not a region. The former idea reflects early translations of the phrase as "Mt. Ararat", which has long been abandoned. I believe rather that the hills referred to in Chapter 8 are those that become covered in Chapter 7, and the "hills of Urartu" simply refers to the "region north of Mesopotamia".

Survivors on the ark

To be succinct, if we take the narrative at face value, then the flood destroyed only the land known to Noah and his family. The world they knew was indeed overcome with water and there was no place to escape. There is no need to speculate, then, how the modern world population was descended from Noah's family, some 4,500 years ago. Or how every terrestrial and avian creature today was descended from a single pair on the ark. Neither must we speculate about how thousands upon thousands of animals fit into the ark, or were cared for, etc., or how Noah managed to seal the boat with tree resin. We need not explain why human occupations are found on 5 other continents, uninterrupted at the time of the flood. Rather, we can focus on Noah, his family, and the creatures of his immediate region (livestock, birds, etc.—note the account does not include the wild beasts like lions, etc.). At this point, the literal reading of the narrative is perfectly in line with the geography, geology, archaeology, and history/literature of Mesopotamia.

Timeline(s) of the flood narrative(s)

How long did the flood actually last? First, God says that after 7 days, 40 days/nights of rain will come (7:4), but then we're told that the waters prevailed for 150 days (7:24). We might say, for example, that it rained 40 days/nights, but that the waters continued to rise from other means (fountains of the deep?). But this creates a problem in chapter 8 (see below). Moreover, Flood geology must allow that rain continued to fall (recycle) throughout the entire event, given the heat of volcanism, tectonics, and the high relative humidity of the atmosphere. If the flood were global, the period of 40 days/nights of rain becomes a physically meaningless figure.

Gen. 8:3 refers to the "end of 150 days", but Gen 8:6 refers to "at the end of 40 days". Does this refer to the 40 days of rain or an additional period of 40 days after the climax of the flood? If it's another period, then it doesn't fit well within the timeline. The text cites 2 1/2 months between the peak of the flood and when the mountains were visible, after which Noah waited 40 days, and released the birds. But it would be another 50 days before the waters finally dried up, and yet 56 more days before Noah and his family exited the ark. I think there is a better solution.

If we unravel the two flood narratives, we find two timelines—each with their own numerical significance. In the first story, there are: 7 days of waiting; 40 days/nights of rain; 7 days of waiting until the dove returns; then 7 days of rest before Noah leaves the ark. Thus there are 54 days of flooding, followed by 7 days of rest/waiting. I'm not big on numerology, but it's worth noting that this equals 6 intervals of 9 days (3x3), followed by 1 interval of 7 days. Some have associated the number 9 with judgment, and of course 7 with heavenly perfection. Regardless, the account breaks down to another 'Creation Week': 6 days of judgment/recreation, followed by a day of Sabbath rest.

I have already noted the canonical tie of this account to the creation/Eden narrative, so I think my analysis could be valid. Of course, it would require the author of J to have known about the 6-day creation narrative (P), contra the traditional Documentary Hypothesis. Perhaps this is weak evidence of an even earlier date for this portion of P? I shouldn't speculate too much!

In any case, the canonical link between the older flood narrative and the Exodus also becomes more clear. In Egypt, God warned Pharaoh (through Moses), before committing to a process of uncreation (the plagues), culminating in death across the whole land to every firstborn. Finally, Pharoah's army is swept away by water (the flood). But God's people spent yet another 40 years in the wilderness and several more in conquest before they could find rest (the "7th day") in the promised land. Moreover, their survival and well being was intimately linked with the tabernacle—a rather out-of-place, rectangular, wooden structure, not unlike the ark.

The second story describes a year-long catastrophe (some say 365 days, or 1 solar year, which is 1 lunar year plus 11 days: 2nd month, 17th day to 2nd month, 27th day—I'm not entirely sure). The exact days of the year are given for the start of the flood, resting of the ark, etc., but not for scientific/technical purposes, I believe. The flood begins on a Sunday (like creation), and the ark comes to rest on what would be preparation day (Friday), just in time for the Sabbath (see Wenham, 1994). God remembers Noah on what would become the Day of Atonement. In other words, this timeline unfolds the antiquity of God's redemption and Sabbath cycle—all in light of the recently established calendar of post-Exodus Israel.

In concluding, I should clarify that I do not propose these accounts contradict each other or that either is necessarily in error. Rather, I think we should allow the possibility that some numbers constituted a literary tool to grab the reader's attention and direct it elsewhere. If I were describing a recent political figure, but prefaced my story with "Four score and seven years ago, so and so first became interested in politics..." you would recognize immediately that I'm not giving a timeline for the figure's youth, but wish to compare their efforts/charisma with that of Lincoln. Although it is possible that the flood lasted exactly 365/370 days, as outlined in the full account, a literal reading of the text (given the style and genre) does not require that we understand it this way.

Post-flood covenants

Perhaps one of the most difficult aspects of the flood narrative to understand from a limited-geography perspective is the covenant made to Noah after the deluge. The question stands: didn't God promise never to do this again? Yet floods approaching this scale have no doubt occurred around the world since Noah's time! That is true, but the dilemma is a two-edged sword, I believe.

A global-flood interpretation would require us to read the covenant as following (paraphrasing, tongue-in-cheek): "Well, the flood you just survived destroyed every individual land animal and bird on Earth, and I promise never to do that again. On the other hand, there will be some pretty heavy flooding in the future that may even wipe out whole civilizations, including yours; but not all of them simultaneously, on the rest of the planet you have yet to discover." There is little comfort to be found in God's promise if we are to read it this way.

Two covenants are made after the deluge: Gen. 8:20–22 and Gen. 9:1–17. Both are tied intertextually to the creation narratives—Gen. 2–3 and Gen. 1, respectively (whether or not one accepts dual authorship is inconsequential to this point). In the first covenant, God promises never to "curse the ground on account of man" again, reversing the curse of Gen. 3 and implying that His creation (land and life) will not suffer on account of man's sin. As an aside, this passage seems to contradict the YEC position that animal death and natural disasters are still a consequence of man's sin, because it would have been reversed at this point. God also promises that the seasonal cycles created to provide man with food and shelter would not be interrupted (a long-standing flood, even 40+ days, would be sufficient to upset harvest for a year).

But in the global-flood paradigm, this again provides little comfort to the primary audience (post-Exodus Israel). Imagine that you are an ancient Israelite, a son or daughter of the Exodus generation enjoying the fruit of the promised land. You have just heard the tale of Noah, as retold by Moses in the Torah. What is the first logical question? I think it is this: if we are unfaithful to God and Torah, will the Lord send the flood waters upon us? Will He destroy the promised land, and all life within, with a flood as in Noah's day? That is the key question, I think, addressed by the record of God's covenant with Noah.

In the second covenant, God reiterates the commission to Noah that was given in Genesis 1: be fruitful and multiply, and I will give you sustenance. But He expands the commission in terms of available food, using language that was very familiar to the priests of post-Exodus Israel (i.e. similar to the law code found later in the Torah). Thus God also establishes the antiquity of His holiness found in Torah. A straightforward reading of the promise to follow (sealed by the rainbow) implies that God would never destroy the land and sustenance given to His covenant people following the flood. Since the time of Noah, Abrahaam, and particularly Moses, God has kept good on this promise. Though Israel would stray, and God would chastise—through conquest and exile—the land and its fruit would never be destroyed by the waters of a flood. It remained the promised land until fulfilled in Christ.

Conclusion

While the story of Noah and his ark has never failed to captivate our young minds, it has remained for many just a story. Centuries of critique from extrabiblical sources have caused many to consign the tale to imagination, hoping that the moral lesson could still 'matter'. Part of this shift, I think, is due to the insistence on reading the narrative as a recent, global flood. For those who recognize the weight of evidence against this claim, a choice between blind faith and reality seems to be knocking at the door.

But I am confident now that the dilemma is indeed a false one. Despite some modern, rigid traditions regarding the historical and physical implications of Noah's flood, the church has never found consensus. Instead, she has struggled to incorporate new evidence over the past two millennia, and so the 'meaning' of the narrative was as fluid as the worldview of the respective reader. We should welcome the evidence from antiquity that is available to us today, limited as it is, to recover the historicity of our beloved Noah.

Taking into account the style and genre of the narrative, as well as the original audience, I believe that a literal reading of Genesis 6–9 fits the available historical, archaeological, and geological evidence. Noah lived in Mesopotamia in the early 3rd millenium B.C. By the providence and mercy of God, he survived a catastrophic deluge and relocated to the highlands upriver. From there, the land was repopulated from the north by many of his descendants. The Semitic influence upon Mesopotamia that followed (~2,650 B.C.) is written in stone and preserved to this day.

Centuries later, God led Abraham out of southern Mesopotamia, toward the promised land. Israel would eventually conquer Canaan, but only after surviving a 'deluge' of their own. Even at her strongest, Israel was vulnerable to the surrounding nations, and again was at the mercy of God for protection and deliverance, not least from the physical elements. But God promised not to curse that land on account of their sin by overcoming it with water. Israel would face punishment and exile, but God would yet preserve His covenant people and the promised land, until all would be fulfilled.


Appendix: the two flood accounts

Consider the natural, poetic flow of the following excerpt. I've taken out only the portions that are hypothesized to be from one of the authors (J, according to Friedman, 1997). Notice also how only the word YHWH is used for God.

7:7, 16b, 10, 12, 17–23; 8:2b–3a, 6

Then Noah and his sons and his wife and his sons’ wives with him entered the ark because of the water of the flood, and YHWH closed it behind him.
  It came about after the seven days, that the water of the flood came upon the earth.
    The rain fell upon the earth for forty days and forty nights.
      Then the flood came upon the earth for forty days,
        and the water increased and lifted up the ark, so that it rose above the earth.
          The water prevailed and increased greatly upon the earth,
            and the ark floated on the surface of the water.
              The water prevailed more and more upon the earth, so that all the high mountains everywhere under the heavens were covered.
               The water prevailed fifteen cubits higher, and the mountains were covered.
              of all that was on the dry land, all in whose nostrils was the breath of the spirit of life, died.
            Thus He blotted out every living thing that was upon the face of the land,
          from man to animals to creeping things and to birds of the sky,
        and they were blotted out from the earth;
    and only Noah was left, together with those that were with him in the ark.
  and the rain from the sky was restrained; and the water receded steadily from the earth
Then it came about at the end of forty days, that Noah opened the window of the ark which he had made;

Obviously, I imposed the chiasmic structure myself, and it could be subjective. But the story moves from the Lord closing the ark to Noah opening the ark, climaxing when the waters cover even the hills, and with a perfect symmetry (keep in mind that the English translation disrupts some of that symmetry). When the other account is isolated, you can see the same symmetry and structure, but it climaxes when "God remembered Noah." To me, this is not only evidence that two stories were redacted, but it also shows the artistic glory of God in uniting the legends of that culture to form a single, inspired text that unfolds God's theological message about judgment and redemption. Feel free to contact me for further discussion about this hypothesis, or a copy of the two accounts separated.

References Cited:

Enns, P., 2005, Inspiration and Incarnation: Evangelicals and the Problem of the Old Testament: Baker Academic, Grand Rapids, 208 p.

Friedman, R.E., 1997, Who Wrote the Bible?: Harper Collins, New York, 303 p.

Heyvaert, V.M.A., and Baeteman, C., 2008, A Middle to Late Holocene avulsion history of the Euphrates river: a case study from Tell ed-D er, Iraq, Lower Mesopotamia: Quaternary Science Reviews, v. 27, p. 2401–2410.

Hill, C.A., 2001, A Time and a Place for Noah: Perspectives on Science and Christian Faith, v. 53, p. 24–40.

Hill, C.A., 2002, The Noachian Flood: Universal or Local?: Perspectives on Science and Christian Faith, v. 54, p. 170–183.

Hill, A.E., 2006, Quantitative Hydrology of Noah's Flood: Perspectives on Science and Christian Faith, v. 58, p. 130–141.

Hill, C.A., 2006, Qualitative Hydrology Of Noah’s Flood: Perspectives on Science and Christian Faith, v. 58, p. 126.

Kline, M.P., 1958, Because It Had Not Rained: The Westminster Theological Journal, v. 20, p. 146-157.

MacDonald, D., 1988, The Flood: Mesopotamian Archaeological Evidence: Creation/Evolution Journal, v. 8, p. 14–20.

Martin, H.P., 1983, Settlement Patterns at Shuruppak: Iraq, v. 45, p. 24–31.

Morozova, G.S., 2005, A Review of Holocene Avulsions of the Tigris and Euphrates Rivers and Possible Effects on the Evolution of Civilizations in Lower Mesopotamia: Geoarchaeology, v. 20, p. 401–423.

Morris, H.M., 1976, The Genesis Record: A Scientific and Devotional Commentary on the Book of Beginnings: Baker, Grand Rapids, 716 p.

Walton, J.H., 2007, Ancient Near Eastern Thought and the Old Testament: Introducing the Conceptual World of the Hebrew Bible: Apollos, Nottingham, 368 p.

Wenham, G., 1994, The Coherence of the Flood Narrative, in Hess, R. S., and Tsumura, D. T., 1994, I studied inscriptions from before the flood. Sources for Biblical and Theological Study: Eisenbrauns, USA, 480 p.

Woodmorappe, J., 1996, Noah's Ark: A Feasibility Study: Institute for Creation Research, El Cajon, 298 p.

Young, D.A., 1995, The Biblical Flood: A Case Study of the Church's Response to Extrabiblical Evidence: The Paternoster Press, Carlisle, 341 p.

Young, D.A., 2004, The Bible, Rocks and Time: Geological Evidence for the Age of the Earth: Intervarsity Press Academic, 510 p.

Tuesday, May 31, 2011

Finding Noah, then and now: Part 1—"Where is Noah today?"

In the beginning

The story of Noah and his ark is one that will never lose its ability to captivate young minds. When I was a child, I regularly reenacted the scene in our bathtub with plastic figures (unbeknownst to my parents, who were paying the water bill!). Not surprisingly, it is one of the first stories taught to young children in Sunday school. Illustrations of a large, wooden boat, filled with all sorts of exotic animals from various continents around the world, are common to our Sunday-school lessons. The ark is pictured floating on an open, boundless sea that covered the whole planet, for at least half a year, until it came to rest on a high mountain peak in the new world. The animals exited peacefully to find new homes, Noah's family set up camp, offerings were made, and the world was replenished and made fruitful once again.

But then something unfortunate happened: we all grew up. Some simply drifted away from the congregation, consigning the fanciful tale to the naïveté of their youth. For those of us that remained in the church, we may have heard the narrative in passing, but rarely as the focus of any single sermon. More than 200 years of historical critical studies and scientific advances incited the world to mock our beloved Noah, and many a preacher would dare not risk controversy by recounting the narrative as historical—or worse, as ahistorical.

The capsizing of Noah's ark?

With adulthood came the responsibility of finishing school and finding jobs in the 'real' world. Most of us, and our colleagues from Sunday school, would end up in a field that cared less about whether Noah really sailed on an ark. But others, like myself, studied geology, biology, archaeology, history, and/or ancient literature. We were told early on that the Earth was never completely flooded, let alone in the course of human history. Moreover, the story of Noah was hardly the first about a man saved by an ark from impending flood waters. Was the Bible guilty of plagiarism? Unless modern scholarship was sorely mistaken about history, we could not maintain publicly our childhood belief in Noah and his ark without facing ridicule. Had the flood of intellectualism finally overcome Noah's ark, more than 4,000 years after the waters receded?

Christians have responded to this dilemma in various manners. Some, through cognizant dissonance, whereby the historical question became irrelevant. Others, through scientific dereliction, whereby the historical question would determine the facts of nature. In the latter case, Christians with scientific degrees formulated the principles of 'Flood geology' and simply reinterpreted geological and archaeological facts to concord with a multifaceted, but rigid axiom: 1) the geologic column and associated structures are the result of a catastrophic flood, ~4,500 years ago, that reshaped the face of the planet; and 2) all terrestrial life, including humans, can be traced to the ark-born survivors of that event.

The failure of Flood geology to explain geological facts has been well documented, not least by geologists in the Christian community. Despite their good intentions, promoters of Flood geology have removed the story of Noah's ark further and further from reality, and thus relevance to the modern Christian. But a high percentage of the Western population is still convinced of its validity, and the movement will, no doubt, continue to grow. While these trends are mutually exclusive, I believe they teach us that most Christians are not satisfied with consigning the Flood narrative to irrelevance. Young-Earth Creationists and Flood Geologists are right about one thing: we should not continue to call ourselves Christians if we believe the story of Noah's ark doesn't matter.

Restoring relevance to the modern Christian

If modern Christians are limited only to the two options above, then we may find ourselves in trouble. How do we approach the text of Genesis 6–9, for example, if we can't teach that it really happened? Moreover, how do we read a text that is more than 3,000 years old, and what kind of relevance could it have today? Are the New Testament analogues of Noah's flood meaningful if the historical referent never existed? These are all valid questions that must be answered by any faithful Christian that wants to remain consistent. But before I attempt to answer them in full, I want to put your minds at ease (in case you had doubts about my own intentions) with the short version.

I will propose that the events of Genesis 6–9 did, in fact, happen. I believe the characters were real people living in a real time and place on our familiar planet. Not only is the story relevant to us today, but we can bridge the cultural gap with some effort. The most difficult challenge of reading a foreign or ancient text does not lie within the text, but within the reader. Since we did not live in the ancient Near East (when the story was originally told), we must prevent our own, modern worldview from being imposed back onto the text—a difficult, if not impossible, task.

Few Christians read the Old Testament with any regularity or depth as it is, let alone the first 11 chapters, and I am willing to bet that most could not distinguish between details from scripture and details from illustrations in Sunday school. The reason is that believers and unbelievers alike have carried with them a Sunday-school version of Noah's ark, and few have reevaluated the text in light of what they know about the world as adults. We need a fresh perspective—a new look at Noah's ark that seeks to do more than stir our imaginations, and keep our attention until lunchtime.

Granted, I am not the first to offer such a perspective, and few of my thoughts here are entirely original. Nonetheless, I find it pertinent to share my perspective as a geologist commenting on faith and science issues. Hopefully, if nothing else, it will guide your thoughts in trying to answer the same questions for yourself.

The appropriateness of using science in understanding the biblical text

Young-Earth creationists will commonly object to the use of modern science in elucidating the biblical text—at least when it means 'capitulating' the face-value meaning. By way of preface, my own conviction is that science is without foundation outside of the God who reveals himself in scripture. I do not pretend that science is a means by which we may critique God, or rationalize the impact of his word. Nonetheless, I am fully aware that science—as a method of knowing the world—must play a part in our reading of his word.

For example, even to answer questions like: How long is a cubit? What are the greater and lesser lights of Genesis 1? How did the author of Genesis measure a year, and how do we convert that to our own calendar? What are the floodgates of heaven? Not to mention, we are dependent on a translation of the Hebrew text, even if we can read Hebrew ourselves. Whether in our use of an archaeological find, or simply a lexicon to look up the Hebrew word, we are dependent on at least some part of science to read and understand God's word.

I begin with these seemingly trivial examples because they are organically related to young-Earth proofs of the flood as a global catastrophe: "How did the flood cover all the mountain peaks? How did the ark land on Mt. Ararat if the flood were not global?"

Assumed in these questions is that Sunday-school image of a large wooden boat, floating on deep, epicontinental seas, which regressed across the globe, eventually to reveal the high peaks of Mt. Ararat. Now, assumptions are not bad (in fact, they are necessary), and I understand how one reasons to this picture. Nonetheless, these challenges use scientific reasoning (namely, the laws of physics and the modern geography of Turkey/Middle East) to make their case. I believe this is no different, qualitatively, from citing geological evidence that a global flood never occurred in recent Earth history.

Literary aspects of Genesis 6–9

Is Genesis myth or history? This question was a chapter title in Peter Enns' book Inspiration and Incarnation. A few friends and I recently finished the book as part of our ongoing book club, and this chapter drew a lot of discussion. It wasn't so much that we disagreed with what Dr. Enns had said—it was how he said it. Are Christians allowed even to use the word 'myth' and 'Genesis' in the same sentence?

Ongoing discussion over what genre characterizes Genesis can be misleading, and stir emotions rather quickly. The reason is that we commonly use the term 'myth' to mean: "an unfounded or false notion." But the primary meaning of 'myth' (especially in literary criticism) is:

"a usually traditional story of ostensibly historical events that serves to unfold part of the world view of a people or explain a practice, belief, or natural phenomenon." (emphasis added)

The latter definition fits Genesis rather well, and thusly Dr. Enns argued. But, understandably, most Christians would not be comfortable with saying "Genesis is myth". Dr. Enns' comments aside, I am willing to say that Genesis falls under the literary category of myth, but also that myth is not mutually exclusive to history. Rather, it is complementary thereto, so the answer to my opening question (myth or history?) is: yes.

When I say "Genesis is myth", I mean that the primary function of the text is not to recall historical events but to unfold the worldview of God's covenant people. We should not read Genesis 6–9 the same way we read Antiquities or Rise and Fall of the Roman Empire. Nonetheless, as God's word, the text is infallible in all it intends to teach us. Thus I believe those historical events were real and did happen. The challenge then, as 21st-century American Christians surrounded by a post-Enlightenment mentality, is to apply proper form criticism both to the text and the reader, that we might unravel the historical particulars and determine what exactly Genesis 'intended' to teach us about history.

In conclusion, and in passing, I do not pretend that I can do this accurately or infallibly. That is why I open my thoughts to discussion. Nonetheless, I will propose now that the 'literal' meaning of the Genesis narrative is far more elusive than others have suggested. Moreover, I am convinced that our modern understanding of the world has been written back onto the text over the centuries, removing us further from the original meaning. I hope to recover at least part of it here.

Genesis 6–9: Why was it written?

The first thing I notice about the flood narrative is its canonical relationship to Genesis 1–3. The passage begins with a rather grim description of the land (6:5): "the wickedness of man was great on the earth, and...every intent of the thoughts of his heart was only evil continually". Man's commission from God was to uphold His image to all of creation, and have dominion over it. But in failing to uphold that image, man has essentially 'undone' the pinnacle of God's creation, thereby completing the first step in a return to the chaos of Genesis 1:2. And so God commits to a process of uncreation (6:7): "I will blot out man whom I have created from the face of the land, from man to animals to creeping things and to birds of the sky."

God's judgment here is justified, in that it follows directly from His curse to Adam (3:17): "Cursed is the ground because of you...". God's covenant people, through Adam, abandoned reconciliation to their God, and brought a plague upon the land by filling it with wicked people (among other things). The curse is lifted at the end of the flood (8:21), when God says, "I will never again curse the ground on account of man...". Eventually, in God's full covenant with Noah after the flood (9:1–17), He restates the commissions given to Adam before the Fall. I argue, therefore, that the end goal of Genesis 6–9 is to return the land to a state of darkness and chaos through judgment, and then bring forth light and life to the land through Noah—God's new Adam.

Both the creation and flood narratives are quite old (primitive, if you will), and may have been around for centuries (in oral or written form) before being penned down as we find them in the received text. But we must keep in mind that each story was told as part of a much larger narrative—the Pentateuch—that was given to ancient Israel. Why, then, were these stories put into scripture? Was it to provide Israel with a divine history book, or remind them what happened long ago? Yes, they are historical narratives, but stories are not told simply to recount history. They are told to place the reader into the story.

Lessons from The Alamo and Animal Farm

My grandfather's family is from Texas, and so naturally, I spent some time reading about the events that led up to the siege of the Alamo. About this time, John Lee Hancock produced his own film portrayal of the battle. I love films about history; I loved studying about the Alamo. I watched the movie, and saw that it was good.

But Hancock's film was not the first about the unlikely birth of Texas. Neither is the Alamo an uncommon tale. In fact, I can simply say "the Alamo" and trust that you know I am referring to a battle, more than a place, and that you already know the outcome. But if we already know what happened, what's the point in making another movie? I suppose there is profit and entertainment, but these motivations are secondary to the storyteller, I believe.

In Hancock's film, we don't just see a reenactment of events. Neither do we see an effort simply to be more 'historically accurate' than others. The characters are given personalities and dialogues—words that may never have been said. Sam Houston likens Santa Anna to Napoleon, and predicts a similar downfall. Jim Bowie's slaves argue the pros and cons of running away, before Bowie sets them free temporarily. Moreover, the film depicts events before and after the main battle, but not necessarily in chronological order and without an explicit sense of the time gap. In other words, Hancock has not retold the story merely as an objectified historiography, but to unfold a particular worldview about freedom, patriotism, family, friendship, race, and empathy with the enemy at our gates.

Hancock's The Alamo is myth. And it places us directly in the story, that we might be inspired to battle our own tyrants and defend freedom at all costs. That is why it can be retold in varied forms to cultures across time and space, with great success.

So what does Animal Farm have in common with The Alamo? Not much really, but there is a common lesson. For the sake of the argument, let's call Animal Farm an allegorical tale, written to critique (negatively) Stalin's communist regime. Since it was first published in 1945 in English, the book has been translated several times into Russian. My wife's senior thesis entailed a literary comparison of three Russian translations of exactly the same English text: one published during Stalin's regime; one in the latest Soviet era; and one less than 10 years ago.

In short, the differences were astounding, despite the fact that each translator was reading the same English text. As you might imagine, the culture and worldview of each translator was evident from the specific words they chose to reflect the English. The earliest Russian translation of Animal Farm, for example, was an allegorical tale, written to critique the tyrannical capitalist policies of the West.

When the Soviet regime was on its death bed, a newer translation told a story about some animals...on a farm. The symbols had been deconstructed entirely. The latest translation, however, was an allegorical tale, written to critique the tyrannical, communist policies of Stalin.

Three lessons, I believe, can be taken from these cases in point. First, we tell stories about the past to comment on the present and prepare for the future. If we want to understand precisely stories that others have told, and particularly if we intend to deconstruct the historical referents of those stories, we must place ourselves in their shoes and ask why the story is being told. Second, the 'meaning' of a single text (or story) is as fluid over history as the worldview of the reader. We will always be inclined to read an ancient story as though it were written specifically to us and for our time. In doing so, we might benefit from the message of the text, but will be blind to its full intentions.

I understand that scripture is unique, in that God is the ultimate author and when we read the 2,000+ year old stories, He is speaking (present tense) to us. Nevertheless, we must concede that just as Christ—the living Word—was fully human and fully divine, so is the written Word (cf. Warfield, 1948, Inspiration and Authority of the Bible; Enns, 2005, Inspiration and Incarnation). The word of our God is alive, and intimately a part of His creation. We confess that God gave his word through real people, in real cultures throughout history, and the words of each author reflected his/her own culture. But we also recognize that this only magnifies our God, who brought himself down to us in such a manner that He could speak and we could listen—despite the fact that His thoughts "are higher than our thoughts."

Lastly, we should recognize that historiography is highly biased and selective. How do you tell the story of the Alamo in under two hours without cutting out 99% of the events? When we come to the biblical text, it seems more like 99.9%. What are we missing, and why were these parts preserved?

Where's Noah?

I believe that Israel, through Abrahaam, was God's answer to the theodicic problem of Adam. God's covenant people deserved judgment, even uncreation, yet He allowed His people to live and renewed His covenant through Noah, to Abrahaam—through whom all the nations would be blessed—and to Israel, Abrahaam's 'seed'. But one major dilemma remained: how could Israel be a solution to the problem if, in fact, they are part of the problem through their own wickedness? Scripture is thoroughly eschatological in this sense (cf. Wright, 1992, New Testament and the People of God).

Reading the Bible, we can find Genesis 1–3 retold again, and again, and again. As such, it is the metanarrative to all of scripture. I already mentioned the canonical relationship of the flood narrative to Gen. 1–3, so consider also how God brings light and life (Abrahaam) out of darkness (the pagan land of Ur) to raise up Jacob (who himself is exiled to darkness but returns with wealth), or to restore Israel from Egypt back to the land of Canaan (the new Eden). At the beginning of the Pentatech, Adam and Eve are exiled from a garden, to which an angel with a flaming sword guards the entrance. Yet when Israel, under Joshua, first crosses the Jordan river, they find an angel with a sword there to greet them, and lead them back to the garden.

Moreover, the promise that the seed of the serpent would always strive against the seed of the woman is fulfilled repeatedly, and God's seed always wins out by crushing the head of the serpent. After the promise is made, we find the first fulfillment in Cain and Abel. God vindicates Abel by cursing Cain and raising up Seth. Immediately after the flood, the seed of the serpent strikes at Noah, but God vindicates Noah by cursing Canaan and raising up Shem's descendants to subdue him. When Joshua leads the conquest of Canaan, he fulfills the promise by crushing the heads, quite literally, of the five kings.

Peter reminds us (2 Pet. 3:5-6) that "by the word of God the heavens existed long ago and the earth was formed out of water and by water, through which the world at that time was destroyed, being flooded with water. But by His word the present heavens and earth are being reserved for fire, kept for the day of judgment and destruction of ungodly men." As sinners ourselves, we are fallen in Adam (Rom. 5) and reserved for God's judgement. Thus when we read the flood narrative today, our primary question should be:

"Where is Noah today? And how do I get on the ark?"

Common to every 'battle of the seeds' from Cain (Gen. 4) to Jerusalem (Matt. 23:37) is that the Lord provides the means of escape, as well as the atonement (cf. Gen. 17). Peter tells us (1 Pet. 3) that Jesus is our Noah, and that by baptism in his name, we might be joined to him and survive the coming flood. Moreover, in every instance of redemption, there is an "already, but not yet" aspect of fulfillment. In other words, God has saved us, but things are not yet put to right, so we still await a future deliverance. Such was the case with Noah; so it is with us.

The Gospel writers present Jesus, I believe, as the climax to Israel's redemptive history. Jesus, the Messiah, is the new Israel. He came to accomplish what Israel failed to do: 1) uphold the image of God to all of creation so that through him the nations might be blessed, and 2) bring it under the dominion of righteousness. "He is the image of the invisible God," Paul reminds us (Col. 1). As such, he is also the new Adam—the true humanity of God—who although tempted with "equality with God" did not grasp as though toward the fruit (Phil. 2:5–7). In Daniel's apocalyptic vision, that one "like a Son of Man" subdues the other nations like beasts. In John's apocalypse, the imagery is no different, and Jesus conquers "the Beast". "All authority in Heaven and on Earth has been given" to Christ, our King, Matthew tells us. Thus Paul, a citizen of Rome, can set Christ up against Caesar (called Lord and Savior), and say "our citizenship is in heaven, from which also we eagerly await a Savior, the Lord Jesus Christ" (Phil. 3:20).

Jesus is the divine solution to the problem in Adam, above all because He was never part of the problem. We cannot, as Christians today, read the flood narrative without seeing this conclusion. We find our Noah today in Jesus the Messiah, and His church is the ark. In him alone can we find shelter and escape God's judgment and survive the flood, that we might return to "Eden"—that is, God's new creation.

Conclusion

Perhaps you are frustrated that I have yet to add anything new to the discussion. So far, I have only preached about redemptive themes in the Bible, and how to relate Noah's tale of survival to our own. Well, that is true, and I hope that if nothing else, my words have served satisfactorily as a devotional to you. The reason I took so much time to expound the flood narrative christologically, however, was to demonstrate how I—as one who accepts the antiquity of the Earth and limited geographic extent of the flood—read Genesis 6–9.

So this is the part where I must ask you, how different is my reading from yours? Granted, I could have elucidated more of the details, but I think my overview sufficiently reveals my hermeneutic, and what I believe is the take-away message of Noah and his ark.

At this point, however, I can almost hear you typing, "What about the details of the flood's extent? The mountains? The animals? All flesh upon the Earth?" Well yes, I have yet to expound what I believe is the 'literal reading' of the flood narrative. That is next. But until then, I wanted to demonstrate why I think those questions are inconsequential to God's message. Was the flood global or local? I don't think it matters. God's final judgment applies to all sinners that hear his message. As one of those sinners, I'm going to find an ark!

None of my theological conclusions are contingent on the exact depth/velocity of the water, sedimentation rate, identification of the pre-Flood/Flood boundary, or the exact length of a cubit. Neither does it matter whether a vapor canopy existed before the floodgates of heaven were opened. Christ's church is my ark.

Should we date the flood using the Masoretic text or the Septuagint? Was it 4,500 years ago or 9,000? Either way, the Lord is my salvation and I will run to the ark. Was Noah's ark nothing but a metaphor, plagiarized from an old, Sumerian myth to keep the Israelites in line? Regardless, I will call upon the Lord, and find rest in His Messiah. There will always be unanswered questions in scripture, but God's message has never been obscure. He alone is our help; our salvation.

-------------------------

Next time, part 2 of 2:

Israel retells the story of Noah: polemical historiography in the heart of Canaan

Wednesday, May 25, 2011

Young-Earth Creationists on a GSA field trip: sand injectites and Flood geology


[This article is in response to a feedback question I received some time ago. The reader brought to my attention several Geological Society of America (GSA) field trips led by a group of young-Earth creationists (YECs) last year. Although young-Earth (Flood) geology was not expressly taught on the field trips, the YEC leaders visited several sites, which they believe challenge the conventional geologic timescale. I spent some time researching the claimed examples of a young Earth, and have focused here on their presentation regarding sand injectites found along the Ute Pass Fault near Manitou Springs, Colorado. Thank you again for the feedback, and I look forward to hearing more of your questions!]

Unconsolidated Earth under pressure: sand injectites in the geologic record

What is a sand injectite? In short, it is a term applied to an irregular sand body—in the form of a pipe, dike, sill, or diapir—that formed when already deposited sand was remobilized in the subsurface. Imagine standing on a sealed tube of toothpaste, and then puncturing the container with a nail, except...while the tube is buried under a layer of mud. The toothpaste, representing unconsolidated sandy sediment, is then injected upward into the overlying sediments. The resulting intrusions have been called sand injectites, sand pipes, clastic dikes, and sand diapirs, depending on their form.

Occasionally, the remnants of injectites are visible at the surface, such as in Kodachrome Basin State Park in southern Utah, or the Panoche Hills in California (Hurst et al., 2011), and outcrop examples have been known for more than 100 years. But geologists have only recently investigated the processes behind their formation. One reason is that the kinematics behind sand injection are difficult to characterize without subsurface imaging and complex physical modeling (e.g. Huuse et al., 2010; Ross et al., 2011)—tools not available to the typical field sedimentologist. Another reason is found in the following excerpt from Schlumberger, a petroleum exploration and production group, who noted:

“Under certain conditions, unconsolidated sand is remobilized and forced upward through overlying layers. Called injectites, these sands can have high porosity and permeability and play a huge role in planning and optimizing hydrocarbon recovery.”

Hurst et al. (2005) echoed these descriptors and determined that sand injectites constitute an excellent, but relatively unexplored, play in petroleum exploration, where hydrocarbon preservation potential was high. For reference, a play in the oil industry refers to a type of deposit or structure (channel sands, dune fields, submarine canyons) that could potentially trap and preserve hydrocarbons (oil and gas). Some major sand injectites, such as in the North Sea, are comprised of well sorted, homogenous, highly porous and permeable sandstones. In the oil industry, these characteristics are of prime importance when it comes to recovering the maximum amount of oil from a reservoir. Thus, sand injectites make ideal reservoir rocks, and their irregular shape aids in trapping oil and gas.

The moral of the story is simply this: petroleum exploration companies have a lot of money, and are willing to spend that money researching aspects of geology that help them better recover oil and gas. Since Dixon et al. (1995) first explored the importance of diapiric sand in petroleum systems 16 years ago, our understanding of sand injectites has grown exponentially.

Modern understanding of sand injection: triggers and fluidization mechanisms

Sand injectites begin as relatively flat (tabular) bodies of sandy sediment, such as those deposited in coastal margins or eolian dunes (e.g. Mississippi River delta and Saharan desert, respectively). During periods of rising sea level, or high subsidence, the sand is overlain by fine-grained muds, or in some cases, evaporites, which may act as a low-permeability seal during burial. Normally, water in the pore spaces of both sediment types would escape as the rock pressure increases, allowing both the mud and sand to compact—the first step of lithification. If the geometry is just right, however, the surrounding mudstone can effectively prevent pore water from escaping the sand body during burial. Not only does this cause the sand layer to become overpressured (a condition that occurs when the pore-water pressure is higher than from the weight of overlying rock alone), but it prevents cementation—the next step of lithification.

Though sandstone lithification essentially halts in the scenario above, the surrounding mud continues to undergo diagenetic modification. First, the mudstone undergoes physical compaction, in which pore water is allowed to escape. At deeper burial (6,000–9,000 ft; 100–110°C), montmorillonite (a common clay mineral) converts to illite. The process involves loss of mineral-bound water to adjacent sedimentary units (fluid migration), as well as volume loss (since illite is smaller), causing clay-rich layers to fracture at depth (Selley, 1998).

Since both modes of compaction cause the mud to shrink, they can potentially undermine the seal that had kept the sand body overpressured. Alternatively, rising hydrostatic pressure in the underlying sandstone will inevitably fracture the mudstone when the upward normal stress overcomes the strength of the cap rock. In either case, high-pressure streams of water are forced upward into the overlying sediments, along with unconsolidated sand. At this point, the extent and geometry of sand injection is only a matter of physics, obviously dependent on the parameters of each scenario (overlying lithology, burial depth, initial hydrostatic pressure, etc.).

To add some perspective, Vigorito and Hurst (2010) reported fluid pressures of ~25 MPa, or 3,625 psi, after mobilization had occurred, and estimated that 27 MPa (~4,000 psi) was necessary to cause fracturing of the mudstone seal. Compare these pressures to the average 30–35 psi in your tires! Scott et al. (2009) estimated subsurface sandstone velocities up to 9.43 m/s, or some 21 mph. Sand injection is no gradual process.

Hurst et al. (2011) summarized a number of proposed triggers for sand mobilization: seismic events, fluid migration, igneous intrusion, and even meteor impacts. These mechanisms are not mutually exclusive to a scenario involving overpressure, however, and are more likely complementary (i.e. the straw that broke the camel’s back; see Huuse et al., 2010). For example, soft-sediment deformation is common in tectonically active regions, like the Late Cretaceous Sevier Foreland Basin of southern Utah, exposed near Cedar City (Parowan Canyon) and Gunlock. If a fluid-saturated sand body is already at high pressure and unconsolidated, even a modest earthquake could set the catastrophic dewatering process into motion.

And for the record: yes, catastrophic processes are perfectly consistent with uniformitarianism!

Sand injectites are dominantly fine to medium-grained, showing graded sedimentary structures that depend on the flow characteristics (banding in lower flow regimes; absence of structure in highest flow regimes; Hurst et al., 2011). Erosion of the surrounding bedrock may also occur. Cylindrical pipes commonly contain fine-grained sand at the core, surrounded by brecciated fragments toward the edge (Hurst et al., 2011).

Young-Earth arguments based on sand injectites

Young-Earth geologists have long argued that sand injectites are problematic for the ‘uniformitarian’ timeline, because they find it inconceivable that buried sand could remain unlithified for thousands to millions of years. Rather, they will argue that sand injectites (and other examples of soft-sediment deformation) warrant a significant rescaling of the geologic timescale—in this case, from hundreds of millions of years to less than 5,000 years. But is the argument premature, given our current understanding of post-depositional sand injection? I will examine two major cases in point here, and conclude that sand injectites are not problematic for the conventional geologic timeline.

Kodachrome Basin State Park, UT
Columnar sand pipes were cited early on as evidence against the conventional geological time scale by Roth (1992), who posited that the Jurassic sandstones of Kodachrome Basin State Park should have lithified (cemented) before the supposed remobilization. He argued that sandy sediments would have to remain unlithified for some 150 million years, based on field relationships. William Hoesch of ICR restated the case here, expressing his doubt with “quotation marks” that sediments remained unconsolidated for more than even 10 million years.

Missing overburden in the Young-Earth timeline

Roth (1992) argued erroneously, however, that movement of the sand occurred as late as Pleistocene, not realizing this would require the process to take place under only a few hundred feet of overburden (i.e. very low pressure). More likely, the sand injected later in the Jurassic (~140–150 Ma; see Netoff, 2002), long before the erosional unconformity at the base of the Upper Cretaceous Dakota Sandstone was formed (~90 Ma). The injectites did not pierce Pleistocene-age sediments, but rather those sediments were deposited on top of weather-resistant quartz arenites of the columnar sand bodies.

Hoesch argued for a Cretaceous-aged injection, based on soft-sediment deformation in the Dakota Sandstone, but the two are not necessarily related. While common in Cretaceous formations in southern Utah, soft-sediment deformation (a typical sign of seismic activity) also occurs in Jurassic units (Netoff, 2002). Both records of seismic disturbance are consistent with the Mesozoic tectonic setting of southern Utah, during which time the Sevier orogenic (fold-thrust) belt was developing to the west.

Despite the uncertain timing of sand injection, it appears to have occurred at least several million years after deposition, based on the biostratigraphic constraints of overlying Jurrasic units. Deposition of the Carmel Formation, for example, is estimated at ~170–164 Ma. Sandstone injectites sourced from the Carmel Formation cut the overlying Entrada Formation, which was in place by 161 Ma. Thus a minimum of ~3 million years passed between deposition and injection. So how did the Carmel sandstones remain unconsolidated for such a period of time?

Salt: geological Tupperware

Evaporite layers, which are impermeable, cap the Carmel Formation locally and could have served as an extremely effective seal during burial. They would also prevent circulation of meteoric water to the buried sandstone. Not only would the Carmel sandstones become overpressured, but pore waters would lack the ions and oxidation state necessary for cementation to proceed. In passive margin sequences, the geothermal gradient is also typically low, so sediments must be buried more deeply than normal to reach a given temperature. Thus quartz cementation would not have occurred before the evaporite seal was broken during burial.

Geophysicist Glenn Morton has similarly commented on the arguments of Roth (1992). He correctly points out that cementation is not simply a function of age, and cites examples from personal experience where deeply buried sediments are still unconsolidated—some below well cemented strata! I will expand on his reasoning later on, with a closer look at cementation processes.

Conclusion

I do not mean to suggest that sand injectites at Kodachrome Basin are not mysterious formations—even counterintuitive on some level. These incredible statues defy tangible experience, and even challenge some very old geological dogmas. But they are not, after all facts are considered, inconsistent with the accepted timing and origin of geological strata. On the contrary, a greater challenge remains to those that believe these injectites formed during or after the Flood, while still unlithified, and yet cemented well enough in the time since the Flood to be exposed as weather-resistant landforms today.

Ute Pass Fault and associated sand dikes near Manitou Springs, CO
Every summer, the picturesque, mountain town of Manitou Springs—located just west of Colorado Springs, CO—hosts a massive tourist population. In addition to the unbeatable scenery, unique shopping experience, and local dining outlets like the Wine Cellar (my personal ‘shout-out’), nearby geological attractions such as Garden of the Gods and Cave of the Winds attract visitors from across the country—myself included (in fact, I spent part of my honeymoon there)!

The structural history of Manitou Springs region is equally enticing. Over the past ~60 million years, the Ute Pass Fault (a high-angle reverse fault) has exposed the Mesoproterozoic Pike’s Peak Granite to the south of the town. Paleozoic and Mesozoic sedimentary rocks were upwarped during the Laramide Orogeny, and are now exposed along the Front Range (e.g. Garden of the Gods). Numerous sand dikes are also found within extensional fractures of the Pike’s Peak Granite. Austin and Morris (1986) note that most dikes are found in the hanging wall of reverse faults along the Front Range, and strike parallel to Laramide faults.

Sand dikes of the Front Range in Colorado are fundamentally different from examples I cited above. Rather than piercing upward into sedimentary strata, these dikes formed when unconsolidated sand moved downward to fill extensional fractures. Nonetheless, sand dikes associated with the Ute Pass Fault are incredible examples of soft-sediment deformation (i.e. remobilization of unconsolidated sand), and are worth exploring further.

Young-Earth Creationists lead a GSA field trip to the Front Range

William Hoesch and other young-Earth geologists led a field trip at the Geological Society of America annual meeting held in Denver last year (Ross et al., 2010; abstract available here). They argued that the Cambrian Sawatch Sandstone injected into Pike’s Peak granite, which was fractured during the Laramide Orogeny and thrust on top of the Cambrian sandstone, some 430 million years after deposition. How did it turn out? One sympathetic spectator noted:

“...a bunch of PhD creationist geologists led a field trip for the premier, annual secular geology meeting. I was there on that trip...and it was like music to my ears to have 16 PhD geologists stumped.”

Austin and Morris (1986) originally advanced the argument that the timing and distribution of the sandstone dikes challenged the conventional geologic timescale. Following Kost (1984), they determined the Cambrian Sawatch Formation (~500 Ma) to be the sediment source based on similarities in textural and compositional maturity (although grains within the sand dikes were better sorted and cemented by hematite, rather than dolomite).

Most peculiar about the sand dikes is that they intrude older igneous and metamorphic rocks (Harms, 1965). Thus extensional faulting (pulling apart) of the crystalline rock was necessary for injection to take place, rather than failure of an overlying seal or cap rock. If the timing of fault formation can be constrained, however, so can the timing of sand injection.

Most injectites are found within proximity to the Ute Pass Fault, a dominantly Laramide structure, and so the timing of injection has been argued to be Cretaceous or later (less than 65 Ma) by Austin and Morris (1986). But if injection occurred as a result of Laramide movement on the Ute Pass Fault, one must explain how sandstone could remobilize after more than 430 million years of burial.

An unrealistic timeline: burial history of the Sawatch Formation

Although no geologist would suggest that lithification is simply a function of time (e.g. Selley, 1998), the proposed 430 million-year time gap of Austin and Morris (1986) would constitute a daunting challenge to the conventional age assignments. The Cambrian Sawatch Formation is not simply old, but it has since been buried by more than 2 miles of sediment. Moreover, there is no impermeable cap rock that would cause overpressuring or prevent circulation of diagenetic fluids.

Austin and Morris (1986) are correct about one thing: the Sawatch Formation could not have remained unlithified until the Laramide Orogeny, unless we are hopelessly mistaken about the age of either event. But the assertion that deposition and injection all took place during or shortly after the Flood is not the only alternative hypothesis. In fact, that scenario is falsified rather easily.

Genetic link between the Sawatch and Fountain formations

The Fountain Formation, also exposed near Manitou Springs, was deposited between the Late Pennsylvanian and Early Permian (Sweet and Sorreghan, 2010). Though dominantly sandstone, the unit is stratigraphically complex, characterized by numerous shallowing-upward cycles. Lithologies range from fine-grained mud, silt and sand to coarse, pebble conglomerates. Sweet and Sorreghan (2010) interpreted both marine and terrestrial depositional environments, and concluded that deposition took place in a fan-delta system, in which uplift to the west drove progradation of sediments toward the marine basin that covered the modern Great Plains.

Based on the geometry of the Fountain Formation, along with clast-size distribution, Sweet and Sorreghan (2010) also concluded that cyclic deposition of the Fountain Formation was driven by movement along the ancestral Ute Pass Fault, during uplift of the ancestral Rocky Mountains. While the Ute Pass Fault exposed near Manitou Springs today is a Laramide feature, the region has been tectonically active since the Cambrian (Myrow et al., 2003).

Conglomerate facies of the Fountain Formation provide further evidence for this depositional model. Sweet and Sorreghan (2010) used petrography to identify earlier Paleozoic clasts within the Fountain Formation, including weathered pebbles from the Sawatch Formation. In other words, the ancestral Ute Pass Fault, also a reverse fault, exposed older Paleozoic rocks as the Fountain Formation was being deposited to the northeast.

The occurrence of Sawatch-sourced pebbles in the Fountain Formation has significant implications for the timing of sand injection, since we may conclude that emplacement of the sand injectites occurred after the deposition of the Sawatch Formation (496 Ma), but prior to deposition of the Fountain Formation (~305 Ma). Moreover, the Sawatch Formation had to be lithified—at least on the upthrown block—before it could erode into pebbles and be deposited in conglomerates of the Fountain Formation. Sand injection did not occur during the Laramide Orogeny, because the Sawatch Formation was already lithified by the late Middle Paleozoic, more than 200 million years earlier.

Syntectonic deposits in a Flood model?

This sedimentological constraint constitutes a major challenge to Austin and Morris’ interpretation of the geologic history, since they must regard both the Sawatch and Fountain formations as Flood deposits. How did the Sawatch Formation lithify within less than a year? And if it did, then how was it injected into the Pikes Peak Granite later in the Flood, during ‘Laramide’ movement along the Ute Pass Fault? Austin and Morris thus face the same challenge they raise, and their interpretation of the sand dikes is simply not tenable in light of all geological data.

But the question still remains: when did sand injection occur? And how did it happen? Not considering the paleogeography and seismic history of the region, Austin and Morris (1986) glanced over the answer in their original paper:

 “Some workers...recognize the fundamental impossibility of keeping the Sawatch
Sandstone...unlithified and deeply buried for 430 million years until the Laramide Orogeny...These workers tend to negate the important field relationships and suggest that the dikes were actually intruded in the Cambrian while the Sawatch Sandstone was unconsolidated. Evidence of Cambrian or Ordovician tectonics of a magnitude able to open up extension fractures hundreds of feet wide, however, has not been found on the Ute Pass Fault.” (emphasis added)

Austin and Morris (1986) thus ruled out the possibility that sand injection occurred in the early Paleozoic (Cambrian/Ordovician) because 1) sand dikes are found along the Ute Pass Fault—a Cenozoic structure; and 2) they believe that only the Laramide Orogeny was powerful enough to form the wide extensional fractures now hosting the Cambrian sand. But there are a few fatal flaws in this line of reasoning.

Tectonic blunders in the arguments of Austin and Morris

Sand injection could not have taken place during the Cenozoic, because uplift of the modern Rocky Mountains was driven by contractional deformation—namely, the Laramide Orogeny. The Ute Pass Fault is a reverse fault, which forms when rocks are compressed together, but sand dikes occur within extensional faults. In the latter case, rocks are pulled apart, so the tectonic features are mutually exclusive. Austin and Morris‘ suggestion that Laramide tectonism was “of sufficient magnitude to open up the large extension fractures” is blatantly contradicted by the field evidence they had already cited. A more parsimonious conclusion is that extensional faulting occurred early in the Paleozoic (Cambrian–Ordovician), allowing for sand injection. Sand dikes were then exposed by uplift and erosion, driven by tectonic contraction, during the Cenozoic.

Austin and Morris (1986) argue that “the coincidence of the dikes along the Ute Pass Fault, a proven Laramide structure, cannot be accidental...”—and they are right. So why should sand dikes be found in proximity to and strike along Laramide faults if they were not formed at the same time? One could answer this question by a simple experiment. All you need to do is take a hammer to a brick, so that it cracks from top to bottom. Then, use a vice to squeeze the fractured brick together until the pieces break and move past each other. As you might expect, the brick will break along already formed fractures (i.e. where it is already weak).

In geological systems, this phenomenon is known as reverse-reactivation of normal faults (e.g. Kelly et al., 1999). During periods of tectonic extension, normal faults and extensional fractures form. Later, when the same rocks undergo compression, reverse faults form preferentially along older fault planes. This process not only explains the association of early Paleozoic sand dikes with Cenozoic reverse faults (namely why sand dikes run parallel to the Laramide Ute Pass Fault) and the high angle of the Ute Pass Fault (in contrast to a low-angle thrust fault), but also solves the apparent time gap of Austin and Morris (1986).

In the citation above, Austin and Morris state that “evidence of Cambrian or Ordovician tectonics...has not been found on the Ute Pass Fault.” I would argue, however, that the sand dikes are themselves evidence of Cambro-Ordovician tectonics! Although most offset on the Ute Pass Fault occurred during the Laramide Orogeny, the fault zone is primarily a Paleozoic structure that also produced thick, syntectonic deposits during the Pennsylvanian (Sweet and Soreghan, 2010) and was simply reactivated in the latest Mesozoic to early Cenozoic.

Conclusion

Austin and Morris (1986) accused earlier workers (e.g. Kost, 1984) of ignoring vital field evidence to save the old-Earth paradigm, but after closer examination, it appears Austin and Morris are guilty the same to support their own claims. In fact, Kost (1984) also used paleomagnetic data from the sand dikes to argue for an early Paleozoic sand injection, but these data were conveniently overlooked.

Overall, sand injectites near Manitou Springs are not evidence for a faulty geologic timescale, as suggested by Austin and Morris (1986). Reinterpretation of the depositional and structural history of the Front Range on a ~5,000 year timeline would create countless geological problems in an effort to solve one or two problems that do not actually exist. In fact, it does not even solve this one or two!

Appendix: Cementation of sandstone
All clastic sedimentary rocks lose both porosity and permeability with depth. Understanding this phenomenon is crucial to the oil industry, since these characteristics may determine whether or not an oil reserve is recoverable. Selley (1998) notes that 1) the geothermal gradient, and 2) the pressure regime are the primary factors controlling cementation during burial.

The sandstone layers that sourced the Kodachrome Basin sand pipes and the clastic dikes near Manitou Springs were deposited in a passive margin and intracratonic setting, respectively. In both cases, the geothermal gradient and sedimentation rate are relatively low, implying that sediments could remain unconsolidated for a very long time.

Cementation also depends on the ion composition and oxidative state of pore waters. Since silica is relatively insoluble at low temperature and neutral pH, sandstone cementation does not occur until deep burial unless ample groundwater is allowed to circulate through the sediments. In some cases, particularly near faults, oxygen-poor waters with high amounts of dissolved iron are introduced to porous sandstones that are already saturated with oxygen-rich, meteoric water. Iron is insoluble in oxidative environments, so the result is a hematite-cemented sandstone, such as in Kodachrome Basin State Park.

In other cases, carbonate-rich waters may circulate down into porous sandstone. Since acidity is lost in the process, the carbonate ions precipitate within pore spaces of the sand, forming carbonate cements. The Cambrian Sawatch Formation was cemented by dolomite, apparently sourced from the overlying Ordovician limestone/dolomite. Sand dikes along the Ute Pass Fault, however, are cemented with hematite—evidence of hydrothermal fluid interaction.

The importance of oil in cementation

If hydrocarbons migrate through unconsolidated or poorly-cemented sandstone, they may prevent further cementation, or even dissolve certain cements already in place (namely hematite). In the American southwest, white, bleached horizons in otherwise red sandstone cliffs reflect this very process. Thus the prevalence of sand injectites as hydrocarbon reservoirs is not entirely coincidental.

Early charges of hydrocarbons are sometimes responsible for exceptionally high porosity and permeability in sandstones. The Coalinga Oil Field of California, for example, yielded far more oil that its counterpart field at Kettleman Dome, because cementation was prevented by an early hydrocarbon charge in the former. If sand injectites were to lack a sufficient seal to preserve hydrocarbons, however, microbially mediated degradation of the oil could lead to rapid carbonate cementation in oil-bearing injectites as they are exhumed (Jonk et al., 2005). Thus many sand injectites and sand pipes are exposed today as weather-resistant structures.


References Cited:

Austin, S.A., and Morris, J.D., 1986, Tight Fold and Clastic Dikes as Evidence for Rapid Deposition and Deformation of Two Very Thick Stratigraphic Sequences, in Walsh, R.E., Brooks, C.L., Crowell, R.S. (editors), Proceedings of the First International Conference on Creationism, Pittsburgh, p. 3–13.

Dixon, R.J., Schofield, K., Anderton, R., Reynolds, A.D., Alexander, R.W.S., Williams, M.C., Davies, K.G., 1995, Sandstone diapirism and clastic intrusion in the Tertiary
submarine fans of the Bruce-Beryl Embayment, Quadrant 9, UKCS, in Hartley, A.J.,
Prosser, D.J. (editors), Characterisation of deep-marine clastic systems: Geological Society of London Special Publication, v. 94., p. 77–94.

Harms, J.C., 1965, Sandstone Dikes in Relation to Laramide Faults and Stress Distribution in the Southern Front Range, Colorado: Geological Society of America Bulletin, v. 76, p. 981–1002.

Hurst, A., Cartwright, J.A., Duranti, D., Huuse, M., Nelson, M., 2005, Sand injectites: an emerging global play in deep-water clastic environments: Petroleum Geology Conference Series, v. 6, p. 133–144.

Hurst, A., Scott, A., Vigorito, M., 2011, Physical characteristics of sand injectites: Earth-Science Reviews, v. 106, p. 215–246.

Huuse, M., Jackson, C.A., Van Rensbergen, P., Davies, R.J., Flemings, P.B., Dixon, R.J., 2010, Subsurface sediment remobilization and fluid flow in sedimentary basins: an overview: Basin Research, v. 22, p. 342–360.

Jonk, R., Hurst, A., Duranti, D., Parnell, J., Mazzini, A., Fallick, A.E., 2005, Origin and timing of sand injection, petroleum migration, and diagenesis in Tertiary reservoirs, south Viking Graben, North Sea: American Association of Petroleum Geologists, v. 89, p. 329–357.

Kelly, P.G., Peacock, D.C.P., Sanderson, D.J., McGurk, A.C., 1999, Selective reverse-reactivation of normal faults, and deformation around reverse-reactivated faults in the Mesozoic of the Somerset coast: Journal of Structural Geology, v. 21, p. 493–509.

Kost, L. S., 1984, Paleomagnetic and petrographic study of sandstone dikes and the Cambrian Sawatch Sandstone, east flank of the southern Front Range, Colorado: Master’s Thesis, University of Colorado, Colorado, 173 p.

Myrow, P.M., Taylor, J.F., Miller, J.F., Ethington, R.L., Ripperdan, R.L., Allen, J., 2003, Fallen arches: Dispelling myths concerning Cambrian and Ordovician paleogeography of the Rocky Mountain region: Geological Society of America Bulletin, v. 115, p. 695–713.

Netoff, D., 2002, Seismogenically induced fluidization of Jurassic erg sands, south-central Utah: Sedimentology, v. 49, p. 65–80.

Ross, J.A., Peakall, J., Keevil, G.M., 2011, An integrated model of extrusive sand injectites in cohesionless sediments: Sedimentology, v. 58.

Ross, M.R., Hoesch, W.A., Austin, S.A., Whitmore, J.H., Clarey, T.L., 2010, Garden of the Gods at Colorado Springs: Paleozoic and Mesozoic Sedimentation and Tectonics: Geological Society of America Field Guides, v. 18, p. 77–93.

Roth, A., 1992, Clastic Pipes in Dikes in Kodachrome Basin: Origins, v. 19, p. 44–48.

Scott, A., Vigorito, M., Hurst, A., 2009, The process of sand injection: internal structures and relationships with host strata (Yellowbank Creek Injectite Complex, California, U.S.A.): Journal of Sedimentary Research, v. 79, p. 568 – 583.

Selley, R.C., 1998, Elements of Petroleum Geology: Academic Press, San Diego, 470 p.

Vigorito, M., and Hurst, A., 2010, Regional sand injectite architecture as a record of pore-pressure evolution and sand redistribution in the shallow crust: insights from the Panoche Giant Injection Complex, California: Journal of the Geological Society of London, v. 167, p. 889–904.

Sunday, May 15, 2011

How old is Carlsbad Cavern (Guadalupe Mountains, New Mexico)?

The Guadalupe Mountains of New Mexico and Texas are home to more than 300 caves, including those of Carlsbad Caverns National Park. If you are not familiar with the geology of the region, the National Park Service has already published a number of brochures describing the intricate, and well decorated cave system (I would recommend starting with this PDF on the development of the caves).

Many visitors and researchers alike have wanted to know, how old are these caves? In the last post, I described the most common method of dating speleothems: uranium-thorium (U-Th) disequilibrium dating. Some of the younger speleothems at Carlsbad Caverns have been dated using the U-Th method (e.g. Polyak et al., 2004; Brook et al., 2006), and cover the past 12,500 years and 164,000 years, respectively. Forty-six U-Th ages were analyzed in the latter case, and were used to model highly variable stalagmite growth (0–70 mm/kyr) and climate over the last two glacial cycles.

But this only address part of the question, because it tells us when precipitation of speleothems began, and not when the caverns were actually carved out. Unfortunately, it is much more difficult to date the removal of something in geology than its appearance (e.g. erosion of the Grand Canyon vs. the sediments being eroded).

The curious case of Carlsbad Cavern: sulfuric acid dissolution

Several researchers in the region devised a novel solution to this question (Polyak et al., 1998). As it turns out, some of the larger caves of the Guadalupe Mountains were dissolved with the help of sulfuric acid (as opposed to just carbonic acid). The unique dissolution process left its mark in the form of sulfate minerals, such as alunite, that formed residues on the cave walls, and in small cavities. Alunite is a potassium-bearing mineral, which means that it can be dated using the 40Ar/39Ar method. Since alunite forms as a byproduct of dissolution, the model age should reflect the time of cave dissolution.

Polyak et al. (1998) obtained 15 ages from the purest alunite samples (determined by XRF), representing 5 different caves in the region. Model ages ranged from 3.89–12.26 million years (precision better than 3%) and were reproducible across multiple rooms from each cave. Moreover, clay minerals from the Permian bedrock were dated by the same method, and estimated to be 278±3 Ma. Several clay-rich samples of alunite, with unusually high K/Ca ratios, yielded anomalously old ages (~30 Ma), as expected. Thus contamination could be ruled out in the primary data set by analyzing for clay content and elemental ratios (K/Ca).

40Ar/39Ar model ages, tectonic uplift of the Guadalupe Mountains, and the age of Carlsbad Cavern

Model ages from each cave were also plotted against elevation, revealing a strong correlation. This result corroborates the current understanding of cave dissolution, which is thought to occur from groundwater interaction near the water table. As the mountains were uplifted, the water table dropped, and so caves were carved out at lower and lower elevations. In other words, the oldest caves are now found at the highest elevation, and the youngest caves are found much lower.

Carlsbad Cavern, currently at ~1,100 meters above sea level, was carved out about 4 million years ago, according to alunite model ages. Speleothems would have begun long after, however, and some are still forming today.

Sulfuric acid dissolution: mechanism of rapid cave formation in a young Earth?

Back in 1998, young-Earth creationist Michael Oard tried to work the results of Polyak et al. (1998) in his favor (original article here; responding to YEC-critic Art Strahler). Mr. Oard suggested that since sulfuric acid is a much stronger acid, it could have formed caves rapidly during or after the Flood, allowing more time for speleothem formation (~4,500 years versus...4,000 years?). Currently, some 10% of the world's caves are thought to have formed by sulfuric-acid dissolution, but Mr. Oard posits that number might be larger, and the evidence has since washed away.

Greg Neyman (Answers in Creation) has already responded to the article here, showing that Mr. Oard's optimism is hardly warranted, so I will address the remaining errors here.

1) Syn-Flood vs. Post-Flood: Mr. Oard suggests that cave dissolution might have occurred during the Flood, contra his critic that deemed caves as "post-Flood" features:

"...cave formation is not necessarily a post-Flood phenomenon as Strahler thought. It could have formed anytime after the limestone was first deposited in the Flood, since hydrothermal water would be expected to begin moving through the limestone soon after deposition."

This point is hardly worth discussing, since it only moves the possible age of the cave back by one year at most. Nonetheless, I'll mention that evidence of hydrothermal fluids is common in limestone bedrock (e.g. Tritlla et al., 2001). Hydrothermal fluids typically move through fractures in the bedrock and deposit calcite veins in their path. The calcite is a mixture of dissolved bedrock and CO2 from thermally altered organic matter. Hydrothermal fluids also contain trace elements, like strontium, that are incorporated into the recrystallized calcite. Overall, hydrothermal activity is very easy to detect in carbonates, because it shifts the chemistry on every level: 87Sr/86Sr ratios drop, along with δ18O and δ13C values. Mr. Oard's hypothesis can thus be tested, but I suspect that most of his readers will rest on his 'just-so' story.

2) Biogenic sulfur: Mr. Oard contradicts himself after he confuses the origin of sulfuric acid in the Polyak et al. (1998) study.

"The sulfuric acid is formed by the oxidation of hydrogen sulfide in hydrothermal water...The 34S/32S ratio indicates the hydrogen sulfide is biogenic."

Polyak et al. (1998) mention sulfur input from hydrothermal fluids as a factor for some caves, but not in the case of Carlsbad Cavern. The significance of isotopically light sulfur is that the sulfuric acid was ultimately sourced from decaying organic matter—not H2S in hydrothermal fluids. Hill (1990), cited by Mr. Oard, linked the biogenic sulfur signal to hydrocarbons (oil) in the underlying strata. In other words, sulfur-bearing oil was oxidized in the subsurface to produce small quantities of H2S, and that H2S was oxidized to sulfuric acid (H2SO4) as it was carried through the groundwater to the site of cave dissolution.

Now, I do not highlight this mistake for the sake of trivial amendment. The fact that sulfuric acid responsible for carving out Carlsbad Cavern was a byproduct of oil degradation raises a serious challenge to Mr. Oard's young-Earth timeline, for it requires that sedimentary organic matter had already matured to oil by the time Carlsbad Cavern was forming. But outside of controlled, high-temperature and high-pressure laboratory conditions, oil does not mature overnight! At the current rock temperature beneath Carlsbad Cavern, the process would have taken many thousands to millions of years. Thus Mr. Oard's assertion that cave dissolution might have taken place during the Flood is entirely contrary to the facts.

In summary, Mr. Oard's timelines does not allow enough time 1) for oil to have matured; 2) for oil to have chemically degraded; 3) for sulfuric acid to be transported to the site of dissolution, let alone dissolve the massive caverns; 4) for the water table to drop substantially, creating a vadose zone environment; and 5) for decorative speleothems (some the size of trees!) to have precipitated.

3) Geochronological mishap: Since my focus here is on the age of Carlsbad Cavern, I will conclude with Mr. Oard's misunderstanding of the available geochronological data. Since Mr. Oard must reject all radiometric dates from cave samples—though he does not explain why, scientifically, we should—he ends the article by blankly asserting that the available data is contradictory:

"It is of further interest that the dating of alunite resulted in significantly older dates for...caves in the Guadaloupe Mountains. The new dates range from 4 to 12 million years (Ma)...Previously, the cavern was dated at 1.2–0.75 Ma, or as much as 3 Ma based on the timing of mountain uplift. The younger dates were not only based on field evidence, but also on paleomagnetic, uranium-series, and electron-spin-resonance dating...This does not give one much confidence in dating methods." (emphasis added)

If you also read my last post, then Mr. Oard's error might seem obvious. Polyak et al. (1998) did not introduce 'new dates' for the cave, as though to correct available ones. Rather, the various studies were dating entirely different events.

Paleomagnetic, U-series, and electron-spin-resonance methods are applied to speleothems or sediments within the caves. The 40Ar/39Ar ages of Polyak et al. (1998) were applied to alunite formed during cave dissolution. Obviously, speleothems and cave sediments cannot form until the cave has actually been carved out, so we would expect these dates to be younger than those for the alunite. Despite the confidence in Mr. Oard's sarcastic assessment, it remains a non sequitur.

Conclusion

The available geochronological data are thus perfectly consistent with conventional understanding of Carlsbad Cavern's geological history. Uplift of the Guadalupe Mountains began some time in the early Cenozoic. In the mid-Miocene, H2S was introduced to the groundwater, was oxidized to sulfuric acid, and began dissolving caverns near the water table. The water table dropped slowly over the rest of the Miocene, and into the Pliocene, carving out Carlsbad Cavern around 4 million years ago. Since that time, continued fall of the water table created a vadose zone within the cavern, allowing for the precipitation of speleothems (as early as 1.2 Ma or more), and that process continues today.


References Cited:
Brook, G.A., Ellwood, B.B., Railsback, L.B., Cowart, J.B., 2006, A 164 ka record of environmental change in the American Southwest from a Carlsbad Cavern speleothem: Palaeogeography, Palaeoclimatology, Palaeoecology, v. 237, p. 483–507.

Hill, C.A., 1990, Sulfuric acid speleogenesis of Carlsbad Cavern and its relationship to hydrocarbons, Delaware Basin, New Mexico and Texas: American Association of Petroleum Geologists Bulletin, v. 74, p. 1685–1694.

Polyak, V., McIntosh, W.C., Güven, N., Provencio, P., 1998, Age and Origin of Carlsbad Cavern and Related Caves from 40Ar/39Ar of Alunite: Science, v. 279, p. 1919–1921.

Polyak, V., Rasmussen, J.B.T., Asmeron, Y., 2004, Prolonged wet period in the southwestern United States through the Younger Dryas: Geology, v. 32, p. 5–8.

Tritlla, J., Cardellach, E., Sharp, Z.D., 2001, Origin of vein hydrothermal carbonates in triassic limestones of the Espadán Ranges (Iberian Chain, E Spain): Chemical Geology, v. 172, p. 291–305.

Saturday, May 14, 2011

How to put the 'paleo' in paleoclimatology: isotopic records from speleothems

Caves are perhaps the most fascinating recorders of Earth's recent climate. Though not the most popular proxy—being stuck in a world of paleoclimatology where tree rings and ice, lake, and marine cores make all of the headlines—caves have the potential to record rainfall and soil data at high resolution for thousands of years. The results are not only locked away in dark rooms, safe from the elements, but are contained within some of the most beautiful rock formations known to us: speleothems.

And that is why we take hammers to them, saw them in half, and mount them on a micro-drilling stage in the isotope geochemistry lab.

Paleoclimate records from stalagmites

By way of preface, I am slightly biased in my attitude, because I've spent the past year analyzing isotopic records from stalagmites around North America. But if you were to consider my position for a moment, I don't think you would disagree. Consider, for example, how a cave forms. Precipitation (or spring meltwater) trickles down through a carbonate aquifer, picking up metal cations (like calcium) and bicarbonate anions along the way. Steady drips of groundwater quickly lose their carbonate concentration to the cave atmosphere by CO2-degassing as they hang from the cave roof (or from stalactites). When the drip hits the floor, further degassing initiates the precipitation of aragonite or calcite (CaCO3). Give the process tens to hundreds to thousands of years, and you have a stalagmite with concentric laminae that reach toward the apex.

As it turns out, the carbon and oxygen isotopic chemistry of the laminae depends primarily on rainfall source and amount, as well as soil activity. We can test these hypotheses by comparing isotopic records from very recently formed stalagmites with human/instrumental climate records, or by comparing the isotopic chemistry of rainwater to dripwater to aragonite in stalagmites over several years. In general, oxygen isotopes are depleted in 18O (heavy oxygen) during wet periods and enriched in 18O during dry periods, but the source of precipitation also plays a role (high vs. low latitude; Atlantic vs. Pacific). Therefore, speleothem records from North America record not only rainfall amount, but migration of the Gulf Stream, El Niño cycles, and other multidecadal oscillations.

Depending on the residence time of the aquifer (i.e. how long, on average, the water takes to get from rainfall to 'cave'-fall), the groundwater will mix thoroughly with that from the past month to the past several years. This means that isotopic inputs from rainfall represent a weighted average for that time interval—good news for the paleoclimatologist. Also, most carbonate ions in groundwater are dissolved within the upper soil horizons during the wet season, so one may track soil processes as well.

Both the hydrological and geochemical processes behind speleothem formation are now very well understood. With few exceptions, stalagmites have been proven faithful proxies of climate. If the sampling process were not so destructive, I believe they would also gain some popularity.

High-resolution age dating of speleothems: answering the 'when' of cave formation

Understanding the climatic significance of isotopic ratios in stalagmites is great, but unless we know when each laminae formed, the records are quite useless. So how does one discern the 'paleo' in paleoclimate? If you've ever had the opportunity to visit a cave set up for guided tours (Cave of the Winds, Colorado and Timpanogos Cave, Utah are on my list), the tour guide likely pointed out a speleothem that had been measured over time: "You see, 50 years ago, this guy was 5 cm shorter! So stalagmites grow about 1 mm per year, and since now it's 105 cm tall, it must have been growing for...1,050 years!"

This approach is simple and intuitive, and in some cases may provide a decent approximation of stalagmite growth. But the fact is, the rate of growth for individual stalagmites can vary over time, due to fluctuations in climate. For example, high amounts of rainfall and soil activity can promote speleothem growth. Low ambient CO2 and high ambient temperature in the cave can also promote growth by increasing the rate of precipitation in each drop. Since we know all of these factors will change over the life of a speleothem, we need a more precise method of dating.

Unfortunately, the popular notion that stalagmite growth-rates are simply extrapolated, like above, has caused young-Earth critics to focus on examples of rapid stalactite growth—some rather odd—to make that case that limestone caves are compatible with a young-Earth, Flood model. But the arguments typically go like this: we know that speleothems can form rapidly under favorable conditions; therefore, all speleothems formed rapidly under favorable conditions. The informal logical fallacy is rarely challenged, because few people are familiar with actual method used to date speleothems.

Uranium-thorium (U-series) dating of speleothems

Most speleothems are originally precipitated as aragonite (calcium carbonate). But like any mineral, the aragonite is bound to contain some impurities. Magnesium, strontium, sodium, barium, and lithium are incorporated in trace amounts. As an aside, the ratio of calcium to these trace elements serves as an independent proxy of climate, occasionally used by ambitious geochemists. One of the most important trace elements, however, is uranium.

Why uranium? Because uranium is radioactive, and decays into thorium at a constant, known rate. By analyzing the current ratio of uranium and thorium isotopes, one can estimate the absolute age of laminae in speleothems. More specifically, the ratio of 234U (parent) to 230Th (daughter) is measured. But the ratio does not change like an hourglass model with time (as in the radiocarbon, K-Ar, and U-Pb systems), since the daughter product is also radioactive, and decays even faster than the parent. Let's take a closer look.

Money matters: a financial analogy
Imagine that you set up a bank account with $1,000 in savings and $0 in checking. Every month, 1% of the savings amount is transferred to checking, but 5% of the checking amount is...donated to charity. In this scenario, the money in savings represents 234-Uranium, and the money in checking represents 230-Thorium. Both accounts are constantly decaying at a constant rate, unique to each account, that depends on the residual balance. The money spent to charity represents the daughter product of thorium decay, which is neither measured in the rock nor this analogy.

At the end of the first month, zero dollars are donated to charity, because the checking account has zero dollars available. But 1%, or $10, will be transferred from savings to checking. The new balance: $990 in savings; $10 in checking. So at the end of the second month, 5% of $10, or 50 cents, will be donated to charity, and $9.90 transferred from savings to checking. The new balances: $980.10 in savings; $19.40 in checking. Easy enough?

In geology, we actually measure the ratio between the isotopes (i.e. $ in savings divided by $ in checking). If we know the rate of decay (what % is lost each month), and the original balance in at least one of the accounts, we can back calculate the time that has passed since the experiment started. Below, I have plotted the experiment over 100 months:


The yellow line represents the ratio between the two accounts. As you can see, the ratio changes very quickly at first, but eventually flattens out to equilibrium (hence the name "Uranium-Thorium Disequilibrium Dating"). This means that if one were to estimate the time passed based on the current ratio between the accounts, that estimate would be more precise at time = 0–30 months than at time = 30–100 months. Correspondingly, U-Th disequilibrium ages are most precise up to ~500,000 years, after which the change in 234U/230Th is too small to be detected.

Another limit occurs in very young samples, since the mass spectrometer is unable to detect thorium at exceedingly low concentrations. Thus ideal samples are uranium-rich to begin with, and are at least several years to several thousand years old. Personally, I have seen very precise (±1%) age estimates from U-rich samples, however, even between 0 and 100 years old.

Depending on the scientific importance of the sample, and given that each age datum costs ~$500 to analyze, between 2 and 20 U-Th dates are taken along the growth axis. This allows the paleoclimatologist to construct an age model for each speleothem, and attach real ages to isotopic records.

But aren't there a few assumptions involved?

Yes, some assumptions are made. That is how science progresses. But fortunately for us, most of those assumptions can be falsified/verified independently.

1) How do we know the initial ratio of U/Th isotopes? In oxic environments, uranium is fairly soluble and thorium is very insoluble. Since stalagmites form out of dissolved constituents of groundwater, we should expect very little, if any, thorium to be originally present (i.e. $0 in checking).

2) Does this assumption always hold? On the contrary, we expect this assumption never to hold, in the absolute sense. There will always be at least some thorium present. So to account for this, we measure the ratio of 238U to 232Th (two common isotopes). Both isotopes are radioactive, but their half-lives (4.5 and 14.05 billion years, respectively) are much longer than that of 230Th (75,380 years), and may be considered stable on shorter geologic timescales. Using the 238U/232Th ratio, the 232Th/230Th ratio, and the total concentration of uranium, we can estimate the initial concentration of 230-thorium. Typically, this value is insignificant, and will only change the age estimates by a maximum of 1% if left uncorrected. To put this in perspective, imagine that I started the experiment above with $1.50 in checking. In this case, the age estimate would be off by less than a few days.

3) How do we know whether any uranium or thorium was lost since crystallization? In speleothems, this is rarely a concern, since most ages fit very well into a growth model (i.e. they get progressively older along the axis, and result in globally correlated paleoclimate records). But if this assumption were challenged, one could use trace element data, petrography, and cathodoluminescence to test whether recrystallization of the speleothem caused a loss of soluble trace-elements. Also, any loss of uranium is likely to be localized, through microfractures in the speleothem. In this case, model ages taken from those points will show up as anomalous, and result in an unrealistic growth-rate curve. It is simply unreasonable to expect that uranium loss occurred systematically, shifting all the ages by a proportional amount.

4) How do we know the decay rates for both isotopes has remained the same? This is a matter of quantum physics, and a sound one at that. There is no reason to expect decay rates to change. If this were to happen, however, during the life of the speleothem, then the growth model would shift dramatically at a point, making it appear as though the speleothem started to grow many times faster or slower.

Are caves and speleothems consistent with the Flood model?

In short, no. The Flood model must consider modern caves and speleothems as post-Flood features. Even if one were to allow for the unrealistic scenario of accelerated nuclear decay during, the caveat would not apply to speleothems. Since thousands of speleothems have been dated beyond 5,000 years, there remains a significant challenge to young-Earth Flood geologists.

We can also consider speleothem records in the larger climatic context. For example, speleothem records match up very well with ice core records (dated by counting annual layers), marine/lake core records (dated by counting annual layers and radiocarbon methods), and tree ring records (same as above). Thus we have multiple independent methods yielding essentially the same result. Such concordance highly corroborates the use of each method to track the Earth's climate history, and thoroughly falsifies the Flood model.