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Wednesday, March 30, 2011

The Japanese tsunami and ICR's 'faulty' understanding of tectonics and uniformitarianism

The calamitous aftermath of the recent earthquake in Japan has, understandably, contributed to countless conversations concerning the proper charitable response, energy policy, and even the humbling power of nature. Nonetheless, I was admittedly surprised when Brian Thomas of the Institute for Creation Research (ICR) published an article entitled Japan Tsunami Demonstrates Destructive Power of Water, in which he conjured a peculiar analogy between those events and his version of the Noachian Flood. He summarizes the relationship as follows:

"If one relatively small earthquake-generated tsunami could cause this much damage in Japan, how much more damage would be caused by the barrage of tsunamis generated by continuous, worldwide earthquakes during the year-long Flood of Noah...?"

Some may question whether it is entirely appropriate to discuss the recent tragedy in light of an act of cosmic judgement, given that many are still in mourning for the losses. I would sympathize with such a reaction, even though I believe it is clear Mr. Thomas did not suggest any theodicean explanation for the events in Japan. That being said, I think it is still worth commenting on whether his proposed geological connection holds up. Do tsunamis hold the answer for interpreting the geologic column as a product of the Flood?

Tsunamis are necessary in a functioning geosphere

Natural disasters do provide an effective teaching tool in geology—albeit too 'close to home' for some—by placing a rather palpable face on otherwise abstract geological concepts. The recent tsunami and previous earthquakes off the coast of Japan are the inevitable result of subduction processes near plate margins. Thick, cold basalt of the Pacific Plate is currently sinking into the mantle, far beneath the eastern coast of Japan. The crustal rocks remain in contact, however, and since this is not a frictionless process, seismic events are frequent. At several miles' depth, the characteristics of the rock are such that significant strain (stretching) can build up, only to be released when it overcomes the shear strength of the rock. If that is not clear, imagine pulling apart opposite ends of a giant taffy bar. If the taffy is too cold (like "just out of the freezer" cold), then it will crack/fragment before splitting. If the taffy is too warm, then it will just keep stretching. Within a certain temperature range, however, the taffy accumulates strain until it snaps, releasing the stored energy all at once.

The magnitude of an earthquake (i.e. the amount of energy released) is a function of the potential strain that can build up before shear failure occurs. Following the taffy analogy, the maximum amount of strain depends on the surface area along a fault plane that falls within a particular temperature range (for silicate rocks, this can fall between ~300°C–600°C, depending on the composition). Suffice it to say that in subduction zones—where both the geothermal gradient (temperature change with depth) and fault dip are relatively low—the maximum potential strain is rather large. Consequently, some of the most violent earthquakes occur at plate boundaries where subduction is taking place.

Although the subduction of oceanic crust results in frequent natural disaster at Earth's surface, it contributes overall to the life of the planet. Subduction zones form island chains and mountain ranges (e.g. the Andes, Sierra Nevadas, Aleutians, etc.) and are concomitant with the creation of new oceanic crust at spreading ridges. Without this tectonic process, Earth's mountains would be free to erode more or less completely, to eventually fill the ocean basins. No subduction, no mountains and oceans. No mountains and oceans, no climate. No climate, no life.

Natural disasters and uniformitarianism

Mr. Thomas quotes Charles Lyell, who originally suggested "the present is the key to the past", to show that uniformitarianism has since accommodated catastrophes like tsunamis and large earthquakes when interpreting the rock record. I think Mr. Thomas would agree, however, that in geologic terms, natural disasters are "everyday natural processes." It is not as though Lyell would object in principle to the interpretation that a turbidite deposit represents a catastrophic, underwater density flow, or that a 5-meter thick lava flow must have taken millions of years to form. Modern geology's objection to Lyell deals rather with his 'big picture' application of uniformitarianism (a steady-state Earth), and is not relevant to the discussion.

Superfaults?

Although the recent earthquake and tsunami in Japan was not the largest on record, or the largest possible, Mr. Thomas is mistaken in terming this a "relatively small earthquake-generated tsunami...". An ~8.9 magnitude quake is still larger than a vast majority of seismic events that occur or ever have occurred. I believe Mr. Thomas might agree with my qualification, so I will note that his relative scale seems to be derived from a misunderstanding of "superfaults". He says:

'...geologists are now talking about metamorphosed rocks bordering ancient fault lines that were caused by "megaquakes" that left behind "superfaults." The superfaults caused so much friction that they melted the rock on either side of the faults, where the rocks rubbed together. Today's earthquake...are not nearly this powerful.' (emphasis added)

Superfaults acquire their name from the exceptionally large displacement that takes place (i.e. where the fault blocks have moved several tens of meters relative to each other), typically as a result of landslide or meteor impact. They are not simply bigger versions, therefore, of earthquakes seen off the coast of Japan, Chile, Alaska, or New Zealand. Superfaults are most commonly associated with caldera collapse, where the emptied magma chamber of a volcano caves in, or meteor impacts, which cause significant displacement for more obvious reasons.

Secondly, the presence of melted rock "on either side of the faults" is not unique to "superfaults", but is found in nearly every fault that cuts through solid rock. Pseudotachylite is the proper term for a rock that has been melted along a fault trace from frictional heating [Note: Not all pseudotachylites are formed by frictional melting, but the term still applies to certain rocks that are]. Other evidences of frictional melting can range in magnitude from a semi-polished slickenside to a meters-thick layer of glass produced along faults near an impact structure.

The amount of fault offset produced by modern earthquakes depends on the cumulative strain (how much energy has been stored), but the movement occurs rapidly enough in all cases that frictional melting can also occur. As with the taffy analogy, rocks in the shallow (i.e. cold) part of the fault are typically too brittle for frictional melting to occur. Instead the rocks break apart to form fault gouge and breccia. But at depth, modern quakes are sufficiently powerful to melt rocks adjacent to the fault. Mr. Thomas is simply mistaken on this point.

The Noachian connection: is the extrapolation justified?

Earthquakes that occur beneath a large body of water (like the ocean) generate fast and energetic waves, which radiate toward coastlines. Since wave energy dissipates during the journey, tsunamis lose their destructive power with increasing distance to the coast. Have you ever wondered, though, why tsunami waves only become destructively significant at the coastal margin? Tsunami waves flood the shoreline because as the ocean water shallows, the wave has no choice but to 'topple over on itself'. If the water does not rapidly become shallow, the tsunami loses its power to 'stir things up' on land. In Mr. Thomas's picture of the Noachian flood, the continents would have already been covered with water (granted, not necessarily at a stand still). What kind of damage does he expect tsunamis to have incurred?

Furthermore, tsunamis come with little warning to the local population, even with seismic stations on constant watch. For many Japanese residents, tragically, one hour's notice was not sufficient to clear the coastline and escape the waves. But in Noah's day, the warning would have been about 59 minutes and 30 seconds less. If Mr. Thomas wants to consider tsunamis produced by the "breakup" of the "fountains of the deep" when interpreting the rock record, he should take into account this observation. Any tsunamis in Noah's day would have been capable of burying artifacts and lifeforms in place, yet no higher animals—including humans—or artifacts—buildings, tools, boats, etc.—are found in a majority of the rock record, if at all. Did life not exist near coastal margins, where it flourishes today? Mr. Thomas's understanding of the Flood is potentially predictive here, but fails to meet that test in the field.

Tsunamis had little effect on the rock record

As long as earthquakes occur at coastal or oceanic plate margins, tsunamis will be a part of Earth's everyday life, so to speak. While tsunami deposits have been found in the rock record (such as those associated with the Chicxulub impact), they are extremely rare. The reason is that more common geological processes (e.g. daily wave action, shifting river channels) are sufficient to rework tsunami deposits before they can be preserved, in most cases.

Mr. Thomas's understanding of the Flood is not corroborated by evidence in nature, even considering the destructive power of water stirred by earthquakes. Moreover, and as Mr. Thomas points out, the evidence of past earthquakes is now preserved along "fossilized faults". But these faults, including pseudotachylites of melt origin, occur in rocks that were supposedly deposited during the flood. How did this happen? For these faults to be preserved—and especially for faults to generate frictional heat and melt the rocks—the sediments must have been lithified (i.e. not unconsolidated, water-saturated grains) and under relatively high pressure and temperature. In attempting to solve one challenge to the Flood model (the origin of wave energy), Mr. Thomas actually raises bigger challenges to that model. The respective solutions, however, are mutually exclusive, and falsify the Flood model as a whole.

3 comments:

  1. Great stuff, Chemostrat. I addressed this issue in my March 2011 PSCF article "Sediment transport and the Coconino Sandstone: a reality check on Flood geology," which isn't available in the full online version until about March 2012, but a text-only version is available here. I created a PowerPoint which summarizes my article on Slideshare.

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  2. Tim,

    Thanks for your kind feedback, and for sharing your work. I loved the article, and found it a very helpful overview on sediment transport, as well as Grand Canyon geology in general. I had previously considered writing about the Precambrian geology of the Grand Canyon, which, as you pointed out, is commonly swept away by Flood geologists. But I think you've summarized the problems sufficiently well that my comments would only be redundant. :) Still, it's encouraging to find someone that's reached similar conclusions regarding Flood geology claims. Thanks again.

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