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Friday, June 24, 2011

Sediment transport during the Flood: qualitative appendix to a quantitative assessment

Did the Noachian Flood deposit the sediments that comprise a bulk of the geologic column? To most of the general public, this might seem a naïve and unsupported hypothesis that was debunked more than 200 years ago. But recent promoters of Flood geology have worked hard to convince Christians that geology still supports the notion of a recent creation and global flood. John Whitcomb and Henry Morris are perhaps best known for reviving the answer to this question in the affirmative, which they expounded in their 1961 publication The Genesis Flood.

Before Whitcomb and Morris, however, Christians had long postulated (i.e. since the early church) that the Flood might explain fossiliferous sediments found high above sea level today. In fact, the ancient Greeks were torn on the issue of whether fossils were remnants of living organisms—in part because they knew of no mechanism that could turn life into stone—and whether the sea had transgressed the land (how would you argue, if you were in their shoes?). Some of the early church fathers offered Noah's flood as a viable explanation to the Greek dilemma. The debate continued until Steno—who finally proved the biogenic origin of fossils to the satisfaction of the scientific community—but early geologists were still unsure how sedimentation worked, and particularly how sedimentary rocks bearing marine fossils could form on mountains! Consequently, Medieval natural philosophers were also inclined to characterize geologic formations in terms of their relation to a global flood in Noah's day.

Were these early hypotheses about Earth history born out of ignorance or incompetence? Not at all. Natural philosophers from Aristotle to Steno did the best they could with the evidence available to them. The only event in history they knew that could bury so many organisms under so much sediment was the Noachian flood. The fact that we were born, coincidentally, many centuries after the tough questions in geology have already been answered does not entitle us to arrogance, or to take pride in 'knowing better' today.

A modern approach to the age-old question

How much sediment could a global flood actually deposit? Early geologists could not answer this question in a quantitative sense. Neither did they know exactly how much sedimentary rock covered the Earth. But after more than a century of exploration and decades of flume experiments, we can at least begin to offer a quantitative assessment.

Sedimentary Rock Inventory

What is the total mass of sedimentary rock on Earth? The exact figure is unknown, but Drever et al. (1988) offered a reasonable estimate that is widely accepted:

Total Mass of Sedimentary Rock: 2.5±0.4 x 10^21 kg

Of which, 0.12 x 10^21 kg (5% of total) lay at the bottom of the oceans today.

Mudstones comprise the majority of this total, followed by carbonates, sandstones, and evaporites. Since sedimentary rock is recycled at plate boundaries (subduction zones), this mass is primarily comprised of Phanerozoic (Cambrian–Recent) sediments, which are considered to be 'Flood' rocks by most YEC's (e.g. Holt, 1996Froede and Reed, 1999; Oard and Klevberg, 2008).

Could a year-long flood have deposited some 2 billion billion tons of sediment? Let's start small, and answer this question in pieces.

Sediment Transport and the Coconino Sandstone: a quantitative assessment

Since young-Earth geologists must consider 'Flood' rocks as water-lain, formations like the Coconino Sandstone—considered to be an eolian (desert, windblown) deposit—must be reinterpreted to fit the Flood model. In response to an article that appeared in Creation Magazine (Snelling, 1992), Greg Neyman argued strongly that such efforts are misguided and ignorant of the physical evidence (Neyman, 2003). Every detail of the Coconino Sandstone corroborates the conventional hypothesis: the sediments were deposited slowly in a long-lived desert that covered much of the western United States.

Tim Helble, a hydrologist, took the argument a step further (technical article available here). If we assume, for the sake of discussion, that the Coconino Sandstone was deposited under water, we can use sedimentary structures (like cross-bedding) to calculate the rate of sediment transport to the site of deposition. In other words, how long would it take just to move all the sand needed to form the Coconino Sandstone? Find out below, in this well-organized slideshow created by Tim:

Keep in mind that this presentation only raises part of the problem: the transport of sandy sediment to the site of deposition. Additional questions remain, which young-Earth geologists must (but cannot) answer. What was the source of such relatively pure and homogenous, quartzose sand in a heavily vegetated, pre-Flood Earth? Why would such rapid and catastrophic deposition result in a formation that is devoid of body fossils from plants/animals (including teeth, vertebrae, and other sand-sized bones)? How could animals leave trace fossils (footprints) if the water was flowing several meters per second? Why doesn't the Coconino Sandstone contain large rip-up clasts from the underlying Hermit Shale (the contact is flat, and even contains mudcracks filled in by sand from the Coconino)?

Finally, the Coconino Sandstone is just one example from the American southwest, and comprises a minor portion of the regional stratigraphy. Mesozoic examples from the Colorado Plateau include the much larger Navajo Sandstone, as well as the Wingate and Dakota sandstones. Why do young-Earth geologists (e.g. Morris, 2010) still insist that these giant formations were laid down in a matter of days, contrary to all the evidence? Because the young-Earth, biblical hermeneutic is remarkably rigid and unrelenting. Though designed to protect the faith from modernism and liberalism, it rather prevents YEC's from witnessing the full beauty of God's creation, while leaving modernism/liberalism unscathed.

Andrew Snelling 'responds'
Although Snelling (2008) does not respond directly to the challenges above, he did provide some comfort to his readers in the form of misdirection. Snelling conveniently ignores the problem of sediment transport by attempting to turn it around on "slow and gradual" geologists. He argues that since the Coconino Sandstone contains detrital zircons from the Appalachians, the situation "poses somewhat of a dilemma...because no known sediment transport system is capable of carrying sand across the entire North American continent during the required millions of years."

Ironically, Dr. Snelling proves the impossibility of such transport with a geographic map of modern North America, on which the Mississippi River drainage basin currently covers most of the continental U.S.! As it turns out, water tends to move downhill, and rivers are perfectly capable of carrying sediments from distant mountain belts to low-lying deserts and coastal plains. During the late Paleozoic and Mesozoic, the Colorado Plateau was near sea-level, and rivers flowed from the Appalachian Range out west toward Nevada (opposite of today). But Snelling continues:

"It must have been water over an area even bigger than the continent. All they can do is postulate that some unknown transcontinental river system must have done the job. But even in their scientific belief system of earth history, it is impossible for such a river to have persisted for millions of years."

Why must water cover an area bigger than the continent for mineral grains to be transported cross-country? Fragments of the Rocky Mountains can be found in the Mississippi River delta today. But I've driven across Colorado and am happy to report: it's not submerged in water!

Sand-sized grains in modern deserts (e.g. Sahara, Gobi, Great Victorian) are commonly sourced from both near and far. The discovery that the Coconino and Navajo sandstones derived some of their material from hundreds of miles distant is hardly surprising. Furthermore, river systems are not always a necessary transport mechanism, since prevailing winds may accomplish the same under favorable conditions (if even from one side of the desert to another). Lastly, I would challenge Dr. Snelling to explain why a continental river system (e.g. Mississippi, Nile, Amazon) could not persist for millions of years. This statement is complete fluff to divert readers' attention from the real issue: even a global flood could not deposit the great sandstones of the Colorado Plateau in less than a year.

Rapidly deposited stratigraphy at Mt. St. Helens

The landscape evolution around Mt. St. Helens has been a favorite topic of young-Earth geologists. In fact, Dr. Steve Austin and others recently led a GSA field trip to the volcano (summary here from Dr. Austin; response here from one attendee), in part to show how rapidly sedimentation and erosion can take place. The unstated argument is as follows:

The eruption at Mt. St. Helens proved deposition and erosion are not always gradual. How effectively, then, could a global flood account for Phanerozoic sediments and subsequent erosion (e.g. Grand Canyon)?

Austin and others thus relied on a subtle 'hook, line, and sinker' tactic to reel others into their own way of thinking (the tactic is more explicit in creationist literature, of course). Nonetheless, they did not fabricate the data. In less than 30 years, Mt. St. Helens did produce thick bodies of fine-laminated sediments, bury entire forests, and carve out a large canyon. So why are 'conventional' geologists yet unconvinced by the arguments of Austin (1986)?

Greg Neyman (2005) answered this question succinctly and accurately: the events at Mt. St. Helens are easily incorporated into uniformitarian models of Earth history, because volcanic eruptions are an 'everyday' part of Earth cycles, geologically speaking. Geologists do not rule out the possibility of rapid deposition/erosion a priori, but rather use the scientific method to treat each case individually (gathering data to falsify or corroborate the initial hypothesis). Consequently, many examples of rapid deposition are known from the geologic column—from tsunami and submarine landslide deposits to meteor impacts to megafloods. On the other hand, young-Earth geologists do rule out the possibility of slow deposition a priori, and commonly distort the facts to corroborate their misguided antithesis.

So how do we tell the difference? Austin (1986) reported:

"[Mt. St. Helens] deposits include fine pumice ash laminae and beds from one millimeter thick to greater than one meter thick, each representing just a few seconds to several minutes of accumulation. A deposit accumulated in less than one day, on June 12, 1980, is 25 feet thick and contains many thin laminae and beds. Conventionally, sedimentary laminae and beds are assumed to represent longer seasonal variations, or annual changes, as the layers accumulated very slowly."

Despite his effort to the contrary, Dr. Austin thus provides good reason to accept conventional age assignments for the geologic column, and interpretations regarding its deposition. Consider the following:

1) Deposits around Mt. St. Helens are rich in volcanic glass and minerals, unlike a majority of fine-laminated mudstones in the geologic record. No geologist denies that volcanic ash can be deposited rapidly—in a matter of hours or even minutes.

2) Fine-grained sand and mud is also known to accumulate rapidly under favorable circumstances (e.g. submarine density flows). But the result is a thin-bedded mudstone that forms unique contacts with the underlying sediment (resembling flame structures) or even antidunes. Shale, on the other hand, forms when relatively flat clay minerals are preferentially oriented as they accumulate slowly in still waters. Both examples are found in the sedimentary rock record (though more commonly the latter), so geologists are not challenged by Austin's claim.

3) Sedimentary structures aside, rapidly deposited mudstones cannot be traced over large distances (such as in the Green River Formation, or even the Bright Angel Shale). Instead, thin beds and laminae will 'pinch out', or disappear laterally, as seen in the Mt. St. Helens' deposits or the experiments of Berthault (summarized by Snelling, 1997).

4) Sometimes, thin laminae result from seasonal effects on the basin (e.g. stratification and overturn of a large lake). But geologists do not simply assume this to be the case. Rather, they use mineralogical, paleontological, and geochemical criteria to distinguish seasonal varves from other phenomena. For example, the concentration of organic matter will vary significantly in varves, along with the carbon, nitrogen, and oxygen isotopic signatures. Major and trace element concentrations should also vary, reflecting a difference in climatic conditions and sediment source during each season (sediments from oxic, river water vs. sediments in the oxygen-poor, deep water). The example of Austin (1986) has absolutely nothing to do with varve interpretation.

5) A 25-foot deposit is impressive, especially for having formed in less than a day, but the sediment transport mechanism is unique to volcanic eruptions: a high-density ash flow. As Tim Helble's presentation demonstrates, similar transport rates in submarine conditions will not produce the sedimentary structures (esp. cross bedding) seen throughout the geologic column.

6) Once again, 25-feet is a lot of sediment. But in some places, Phanerozoic sediments are more than 5 miles thick, not including the sediment removed by unconformities! Austin's explanation would require deposition to occur at several times the rate seen at Mt. St. Helens, every day, for an entire year, while sorting thousands of fossil assemblages into precise, stratigraphic intervals. The stratigraphy of Mt. St. Helens does not provide a viable analog for this speculative, impossible scenario.

Heterogeneity of the Geologic Column: a qualitative appendix

The two examples above provide YEC's with the best possible data to explain sedimentary strata in terms of rapid deposition. Large sandstone units like the Coconino and Navajo contain obvious evidence of fluid flow, which is ubiquitous throughout the formations. Likewise, sedimentary structures in deposits around Mt. St. Helens are relatively homogenous. Whether slow or fast, a single mechanism seems to be responsible for the deposition of each unit.

By mechanism, I am actually referring to what is called the flow regime. A flow regime is defined by the physical characteristics of the fluid: how deep was the fluid and how fast was it moving? Based on flume experiments, geologists can interpret the flow regime using grain size and sedimentary structures (e.g. as was done for the Coconino Sandstone in the slide presentation above). Conversely, variations in grain size and sedimentary structures indicate when the flow regime changed during deposition, and by how much.

A quick look at strata in the Grand Canyon reveals that even if deposition were rapid and catastrophic, the flow regime must have changed many times. Below is a picture of the Supai Group, comprised of alternating limestone, shale, siltstone, and sandstone.

View from the South Rim. Late Paleozoic strata from the Supai Group in the foreground.

Whatever mechanism was responsible for deposition, the depth, direction, and rate of flow must have changed many times to produce such a heterogeneous body of sediment. Moreover, the respective sediment sources must have been geographically distinct (i.e. limestone from one region; quartz sand from another). There is no reason, hydrodynamically, that carbonate sediments would separate from siliciclastics, particularly because carbonate grains range in size from clay (micritic mud) to sand (ooids) to pebbles (shells, intraclasts and oncoids). But if the flow regime and sediment source were highly variable over the duration of the Flood, why do we find sand, shale, and carbonate bodies like these that can be correlated across continents?

Microfacies of Carbonate Rocks

Austin (1990), and a feedback article from Creation magazine, posited that thick layers of carbonate rock (limestone, dolostone) were also deposited rapidly. Austin (1990) said that prevailing currents during the Flood may have transported massive quantities lime mud and its constituents from the sea to the continents. He even cites evidence of fluid flow that is meant to contradict that conventional interpretation of limestone formations in the Grand Canyon. His understanding seems to be, however, that according to conventional geology, all limestone was deposited in "calm, placid seas."

This generalization is misleading, since most limestones are interpreted to have been deposited in very shallow water (less than 200 meters, but usually less than 10 meters). Carbonate sediments are just as susceptible, therefore, to waves and currents. Consequently, most ancient limestones contain sedimentary structures like cross-bedding, horizontal bedding, mud drapes, and rip-up clasts. Others contain evidence of subaerial exposure (dissolution cavities, mudcracks) or long-term interaction with microorganisms (microbialites, stromatolites, thrombolites, oncoids, bioturbation). Carbonate rocks are thus divided into microfacies, based on composition, structure, and fossils. Each microfacies reflects different conditions (water depth, velocity, salinity, etc.) at the time of deposition.

Below is a combination of two photos taken near Timpanogos Cave, Utah (my apologies for no scale; each photo covers a little more than 1 square foot). In the photo on the left, the upper layer contains rip-up clasts (>2 cm diameter) of lime mud. The name of this rock is intraclastic rudstone. For mud clasts to be incorporated, the sediment had to be deposited 1) in a current; and 2) within proximity to a layer of weakly cemented (and dried) lime mud. But if the current were too strong, the finer-grained matrix (i.e. the dark material between mud clasts) would have remained in suspension. If the fragile mud clasts came from a long distance, they would have been destroyed during transport. Modern, shallow, carbonate platforms provide a viable analog for this type of deposition (specifically, the intertidal zone). Flood geology, on the other hand, finds itself in a conundrum. Why does the intraclastic rudstone comprise such a thin layer, distinct in every physical aspect from the surrounding carbonate sediments, if sediments were being deposited so rapidly? What is the source of these fragile mud clasts if the whole land was submerged?

Carbonate rocks near Timpanogos Cave, Utah, illustrating the microscale, sedimentological diversity of carbonate rocks. Each photo is approximately 1 square foot.
In the photo on the right, thin bedding is visible in the top and bottom layers, indicative of gentle currents that sorted the fine-sand-sized particles. In the middle, a coarse shell hash represents higher energy conditions, but with little sorting of the grains, which range from less than 1 mm to more than 2 centimeters across. The dark-gray/tan bed near the bottom is an oolitic packstone—a somewhat muddy, carbonate beach sand. Each facies suggests deposition in the shallow subtidal zone (<10 meters water depth at any time; below low tide), where sand bars constantly prograde across the shallow platform. Once again, Flood geology cannot account for the sedimentological diversity of this rock, because rapid deposition cannot separate these sediments with such precise detail in a matter of minutes.


Only long-term, prevailing currents can deposit homogeneous sediments (like the Coconino) across the face of a continent in a global flood scenario. In response, YEC's propose that large-scale, regional currents were responsible for depositing extensive, tabular beds of sandstone, shale, and limestone. But such currents cannot account for the heterogeneity found in the layers of the Bright Angel Shale, Supai Group, and other formations. Consequently, YEC's must also argue that repeated transgression, regression, and periods of 'stand-still' occurred amid the flood, wherein sediments of differing clast size and composition could be deposited between larger waves. But if continuous, prevailing currents are not sufficient even to carry the sediment required even for the 150–500 foot-thick Coconino Sandstone within a full year, how can Flood geologists explain the remaining miles of sediment in the Colorado Plateau?

The challenge grows immensely when one examines the microscale heterogeneity in sedimentary rocks (carbonates in particular). Catastrophic, sediment-choked currents would have had zero time to slow down, change directions, or stop completely. Therefore, Flood geology cannot satisfactorily explain the range of geological data as a unified theory. But unfortunately, Flood geologists continue to mislead amateur readers by explaining various phenomena in isolation from the relevant data. The result is a confused populace, seeking only to reconcile their faith with the facts of nature. Such misplaced trust is unhealthy, in my opinion, for the future of public/private education, the scientific community, and especially for the church.

References Cited (but not linked):

Drever, J.I., Li, Y.-H., and Maynard, J.B., 1988, Geochemical Cycles: The Continental Curst and the Oceans, in Gregor, C.B., Garrels, R.M., Mackenzie, F.T., Maynard, J.B., [editors], Chemical Cycles in the Evolution of the Earth: John Wiley & Sons, New York, 276 p.

Thursday, June 23, 2011

Grand Canyon, AZ to Logan, UT — A Geology Photo Tour

I've decided that this blog has too many words!

So to compensate, I have littered this post with geology-related photos from the past month. These pictures are in no particular order (chronological, geographic, or even logical), so forgive the randomness. Click on the pictures to view in full size. Also, please feel free to share, but link to the original source if applicable. Enjoy!

Antelope Island, Utah

Antelope Island is well known for its population of American Bison. This bison is grazing on vegetation that is growing in Holocene lake sediments, which formed during Lake Bonneville's life and fall (esp. ~12,000 B.C. to present). Quartzite boulders, like those in the background, litter the landscape, and have eroded from nearby outcrops of the Cambrian Tintic Quartzite (equivalent to the Tapeats Sandstone of the Grand Canyon). If Lake Bonneville were to refill, large boulders such as these would be found amid 'calm-water' sediments. These sediments overly much older sedimentary/igneous rock, but are separated from them by an erosional unconformity. A similar phenomenon is found at the base of the Grand Canyon, where Proterozoic Quartzite boulders are cited as evidence for catastrophic deposition by young-Earth (Flood) geologists.

The bedrock of Anteleope Island ranges in age from Mesoproterozoic, igneous basement (Farmington Canyon Complex) to Cambrian sedimentary rocks. Sandwiched somewhere in the middle (and beneath the bison in this photo) is a Neoproterozoic diamictite. This particular diamictite preserved evidence of glaciation from one of the Cryogenian 'Snowball Earth' events, during which glaciation extended to the tropics. At that time, Utah formed the northern shore of a large, equatorial continent.

A granodioritic gneiss boulder of the ~1.8 billion-year-old Farmington Canyon Complex, which comprises the basal outcrop of the Wasatch Range and a bulk of the basement rock for northern Utah.

Eastern shores of Antelope Island, and a great example of Walther's Law of Facies in action. As the lake recedes, marshland will advance over what used to be shoreline and lake-bottom sediments. Thus a geologic cross section of the region will reveal a transition from fine-grained, calcareous mudstone to oolitic sandstone to organic-rich, calcareous siltstone with fragments of grasses/shrubs. Each layer will appear to be flat, when in fact deposition occurred in adjacent environments on a gentle slope.
Why are sedimentary rocks so flat? Despite the relief generated by the bounding mountain ranges, most sedimentary basins are extremely flat. Since topographic highs (i.e. mountain ranges) provide sediment to the basin, they will not be preserved in the geologic record, except as detrital fragments in the valley sediments. With the aid of radiometric dating, geologists study the composition of sedimentary rocks through time to reconstruct the tectonic (or structural) history of a sedimentary basin. 
Shoreline sands in the Great Salt Lake are comprised of oolitic carbonate (i.e. tiny snowballs of calcium carbonate). Minor sand bars, seen above in the foreground, will form thin sets of oolitic grainstone (limestone) with low-angle cross bedding. Thin lenses of silty mudstone should also form between bed sets, as wind and stagnant water cover the sand with dust between storms. Avian footprints are common on the beach (namely, seagull). Although wave action commonly erases the visible evidence, prints of the heavier gulls will be preserved a few centimeters below the surface as carbonate grains/mud are compacted beneath their feet. One time, I found the fully articulated skeleton of a seagull (meat-free, but a few feathers still intact) buried in the carbonate sand. How are bird skeletons (e.g. Archaeopteryx) preserved in lake carbonates? Now I know! Fossilization requires 'rapid' burial, but not that rapid.

Bingham Canyon Copper Mine (Rio Tinto/Kennecott), Utah

Difficult to describe or capture in a single photograph. This mine is big— the largest open-pit copper mine in the world, in fact. In addition to copper, the mine produces economical supplies of gold, molybdenum, and sulfuric acid. Yes, I learned that from the video in the visitor's center...and a personal tour through the core lab!

Up, down, up, down—non-stop delivery of ore and waste. Note the bulldozer and full-size pickup for scale.

Timpanogos Caves, Utah

American Fork Canyon, as seen from the entrance to Timpanogos Caves. When the caves first formed (some half a million years ago), they were at the same elevation as the river. Coincident uplift of the Wasatch Range and downcutting of the river, however, have since separated the two by ~1,000 vertical feet. Flowstone and riverine sediments within the cave were dated to estimate rates of uplift (less than 1 mm/year, on average).
Helictites and soda-straw stalactites. Variations in climatic conditions (temperature, humidity, precipitation, soil activity) can affect the rate of dripwater flow and calcite precipitation within a cave. This results in seemingly stochastic growth patterns for individual speleothems, pictured above.
When the tour began, we were asked: "What would you do if you found a cave like this for the first time?" I responded, "Take samples!" I don't think the tour guide like my response, but I make no apologies. I would love to take either of these currently forming stalagmites back home with me—well, to the lab, that is. Each stalagmite is about 1.5–2 meters tall.
The inevitable collision course of speleothem formation. Some things just don't last forever...
The closest thing left to 'pristine beauty' in Timpanogos Caves. Not much else to say, except that the 'night' setting on my wife's camera added a very special effect from the artificial lamp placed by the park service.
Brecciation and recrystallization of the host carbonate. When these rocks were deeply buried, the weight of overlying sediment caused the brittle carbonates to fracture. Subsequent fluid flow allowed for the reprecipitation of relatively pure, white calcite (compared to the dark, organic-rich limestone/dolostone surrounding). In other words, these rocks have been lithified for a very long time.

East Canyon Reservoir, Utah

A great day of fishing, interrupted briefly by a dark rain cloud. The positioning of the cloud caused the Wasatch Range (background) to appear rather surreal.
The red conglomerates that outcrop near I-80/I-84 in northeastern Utah are synorogenic to the Sevier Fold-Thrust Belt—a mountain range that runs north-south through northern Utah, southern Idaho, and western Wyoming. During the Late Mesozoic, sedimentary rocks in this region were 'squeezed' together by tectonic forces, causing them to be folded and thrust on top of each other (see cross section here for a more graphic depiction). Pebbles and boulders that comprise the conglomerate above are weathered fragments of earlier Mesozoic and Paleozoic rocks. In other words, the underlying rock layers must have been fully lithified before this conglomerate was deposited in the Late Cretaceous. Since that time, more than a mile of Cenozoic sediments accumulated over the conglomerate before it was exposed here. Synorogenic deposits provide the clearest evidence, I think, for the antiquity of the geologic column. 

Cache Valley (Logan), Utah

May in Cache Valley: ample snowmelt for the summer.

Fault scarps and lacustrine (lake shore) benches are common sights along the Wasatch Range. Can you pick them out?

Layton, Utah

View south toward the Oquirrh Mountains (west of Salt Lake City), which overlook Magna, UT and the south end of the Great Salt Lake. 
The windows of heaven. Antelope Island seen at the bottom right.

Grand Canyon (south rim), Arizona

Outcrop of the Kaibab Limestone, which was deposited in shallow marine conditions during the Permian (~260 million years ago). Four different carbonate lithofacies can be seen in this photo alone, each representing a different depositional environment and different flow regime (i.e. water depth/velocity). The heterogeneity of Grand Canyon sediments has long been overlooked by Flood geologists, who have mistakenly proposed that catastrophic slurries of lime mud and seashells could account for thick carbonates like the Kaibab. Each carbonate layer above differs in 1) grain size and composition, 2) clay vs. carbonate content, 3) cement type and composition, and 4) fossil type and abundance. These differences cannot be explained by hydrodynamic sorting alone (many features, like oncoids, result from algae/bacteria living in the sediments for years). Sedimentary structures provide evidence of weak tides and waves, or even subaerial exposure, but not catastrophic flow in deeper water.

Supai Group (late Mississippian to early Permian). The 'step-like' slope at the base of the picture results from alternating fine and course-grained carbonates and mudstones of the Watahomigi Formation. The cyclic pattern is interpreted to result from 1) long-term variations in sea-level; 2) progradation of carbonate sand bars (think modern Caribbean); or 3) (more likely) a combination of the two. The semi-arid climate of southern Nevada has similarly produced excellent exposures of cyclic carbonates, bearing testimony to a time when a dynamic sea transgressed most of the western United States.

Well, that's all for now! Perhaps I should do this more often? Geology is always explained most effectively by pictures, in my opinion. I welcome any feedback (or corrections?) or additional photos that you'd like to share. Again, please feel free to share any pictures you find here, but link to the original source if applicable (i.e. if reposted online).

Wednesday, June 15, 2011

Coming up short: Coal beds and the "Pre-Flood Biomass"

One remarkable topic within Flood geology is that of the pre-Flood biomass—that is, the total mass of organisms (alive or dead) on Earth before Noah's flood. In addition to explaining a water source to cover the whole Earth and a sediment source to supply the Phanerozoic rock column, young-Earth geologists must also explain how the entirety of fossilized organisms existed simultaneously on Earth at the onset of the Flood. Impossible, you say? In Flood geology, there is always an explanation.

I won't delve into the details of young-Earth arguments, however, because I don't think it is necessary. In short, Flood geologists believe that all fossils* (from frustules to shells to molds to bones) represent organisms that were alive or recently deceased when Noah's flood began (e.g. Snelling tackles the chalk issue here; see also Greg Neyman's brilliant, succinct response here). Petroleum reservoirs (coal, oil, and gas) are also assumed to be dominantly biogenic, and thus from pre-Flood plants, algae, bacteria, etc. Adding up these figures would result in a rather crowded planet, but Flood geologists assure us that climatic conditions prior to the flood were more favorable to life than today, and so Earth could accomodate such a population.

Supplying the world with coal

Dr. Andrew Snelling reviewed the particular case of coal in an article posted here from 1986. Although he concludes that Earth could sustain forests capable of supplying the world's coal reserves, his argument assumes some rather arbitrary or inaccurate conditions. For example, he uses a compaction ratio of less than 2:1 from vegetation to coal, meaning that it would take less than 2 meters of raw vegetation to produce 1 meter of coal. His reasoning was based on "modern research," which "shows that less than two metres of vegetation are needed to make one metre of coal," but he fails to cite the supposed research. As it turns out, the compaction ratio of peat to coal is much lower than geologists originally thought, but peatessentially a type of soil—is very different, qualitatively, from catastrophically buried, raw vegetation.

Dr. Snelling also supposes that the pre-Flood land surface was approximately twice that of today. "If then this vast land area was under lush vegetation," he says, "then we can account for 100% of the known coal reserves." But this scenario is not only falsified by Precambrian stratigraphy (which is dominantly marine and quite extensive), but would result in a far more arid landscape (i.e. less ocean = fewer big storms; greater average distance to water = more continentality). Vapor canopy, you say? We'll leave that one to the jury.

An article by Gerhard Schönknecht (1997; posted by CMI) analyzed the problem with more depth and honesty, but still relied on highly improbable conditions (e.g. 40% thick-forest cover over the entire Earth; near perfect preservation). Could a pre-Flood biomass account for all the coal beds on Earth? Well, perhaps...but as I said, that question is rather inconsequential to a much larger problem.

Carbon conundrum

Discussions on whether a pre-Flood biomass could supply organic carbon to the world's coal reserves are simply misguided. Why? After explaining the origin of coal, one must account for the organic carbon in all other petroleum resources, from oil to asphalt to natural gas. Furthermore, one should account for the fact that most oil/gas/coal was never preserved or has been eroded out since deposition.

After these masses are summed, one should factor in that this accounts for only 0.13% of all organic matter buried in sedimentary rocks (nearly every sedimentary rock contains some organic matter, if only 0.01%).

So where did all the carbon come from? Ultimately, today, it comes from CO2 in the atmosphere. Can we assume photosynthesis occurred before the flood? If so, the drawdown would have been so great that one must posit an extraordinary source of carbon, several thousands of times larger than today, to the atmosphere. Flood geologists have yet to create a viable, pre-Flood carbon cycle that explains both fossil biomass and isotopic values of organic matter and carbonates.

The real 'pre-Flood biomass'

How much organic carbon is actually in the geologic column? Holser et al. (1988) provided the following estimates:

Fossil Fuels:
Bitumen (recoverable coal/oil/gas): 11,400 Gigatons Carbon

Other Sediments:

Pelagic ocean sediments: 756,000 Gigatons Carbon
Unlithified shelf/slope sediments: 4,400,000 Gigatons Carbon
Sedimentary rocks: 9,000,000 Gigatons Carbon

Total Exogenic Organic Carbon: 14,160,000 Gigatons Carbon!

Let's compare that to nowadays:

Modern Biomass (living and dead): 4,400 Gigatons Carbon

In other words, the amount of organic carbon on the surface of the Earth is more than 3,000 times that found in the entire modern biomass. If every organism on Earth (dead and alive) was suddenly buried in a flood and swept to the bottom of the ocean, the amount of organic carbon transported to the deep ocean would equal less than 1/170th the amount already buried in its sediments.

Might I suggest approaching Genesis with a less anachronistic and lexically rigid hermeneutic?

*Although I say "all" fossils and petroleum reservoirs, it depends on where one assigns the 'pre-Flood' and 'post-Flood' boundaries. To be fair/accurate, I should say Cambrian–Cretaceous at minimum, but I think the point is inconsequential to my argument.

References Cited:

Holser, W.T., Schidlowski, M., Mackenzie, F.T., Maynard, J.B., 1988, Biogeochemical Cycles of Carbon and Sulfur, in Gregor, C.B., Garrels, R.M., Mackenzie, F.T., Maynard, J.B., [editors], Chemical Cycles in the Evolution of the Earth: John Wiley & Sons, New York, 276 p.

Wednesday, June 8, 2011

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


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.


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.