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Friday, March 28, 2014

The Great Salt Lake: Monument to Stagnation

Reflection of the Wasatch Mountain Range (northern Utah) in the Great Salt Lake. American Bison are visible grazing near a pond at the right edge of the photo. View east from Antelope Island, just west of Farmington, Utah.

Any review of the literature by so-called "Flood Geologists" will yield a plethora of hyped-up examples, in which catastrophic geological processes supposedly occurred at warp speed in the recent past. Steve Austin's "Grand Canyon: Monument to Catastrophe" now serves as a template for reinterpreting the past to conform to an oversimplistic reading of Genesis. But closer analyses of these pseudoscientific works, which fill article databases at Answers in Genesis and Creation Ministries International, invariably reveal fundamental errors in data interpretation, and so the effort continues to battle the spread of misinformation by ostensibly evangelistic organizations.

During a recent trip to northern Utah, however, it occurred to me that these article databases are lacking a vital bit of context: the fact that for every geological example for which 'recent catastrophe' could plausibly be argued before a non-specialist audience, there exist one million examples for which catastrophic processes make absolutely no sense. The Great Salt Lake is one such candidate.

The modern Great Salt Lake, situated in the northeastern Basin and Range province of the western U.S., is but a modest residual of glacial Lake Bonneville. If you're unfamiliar with Bonneville's history, I recommend that you take an interactive tour here, courtesy of USGS. Since the peak of the last ice age, the lake's water level fell a little more than 300 meters, causing isostatic rebound of the underlying crust. As the weight of the water disappeared, in other words, the ground elevation rose several meters in response (similar to what happened in post-glacial Scandinavia to produce the fjords, but on a smaller scale).

When did all this happen?

Along the Wasatch Mountains and other elongated ranges of northwestern Utah, multiple terraces mark previous highstands in the stepwise transition from Lake Bonneville to the Great Salt Lake. The earliest dating of these shoreline sediments indicated that maximum water levels coincided with peak glacial conditions between 25,000 and 14,000 years ago (Broecker and Orr, 1958). These authors hypothesized early on that the water level tracked regional climate changes in the Great Basin, with cooler and wetter glacial conditions promoting higher lake levels.

Later radiocarbon dating confirmed and expanded upon early results (Oviatt et al., 1992), after a suite of geophysical tools were employed to reconstruct lake levels and water chemistry by comparing sections of sediment across the basin (e.g. Spencer et al., 1984). These studies revealed long periods—centuries to millennia—during which either a high-standing freshwater lake or a moderately low-standing saltwater lake prevailed.

Why should we trust the radiocarbon dating?

Putting a young-Earth spin on Lake Bonneville would involve reinterpreting radiocarbon ages to reflect the early 'post-Flood' period when atmospheric 14C was supposedly equilibrating to modern levels. In other words, the AiG and ICR crowds would consider these radiocarbon dates to be apparently old, because in their view, the lake must post-date Noah's flood. Cramming the long history of Lake Bonneville into a few hundred years, however, would result in a nonsensical portrait, in which the sediment deposition rate no longer corresponds to the inferred climate and water-level. For example, Oviatt (1997) correlated lake-level shifts to global climate changes recorded in North Atlantic sediments, the Greenland Ice Sheet cores, and numerous cave and lake records. These various geological records are all dated by different techniques, so any young-Earth twisting of radiocarbon dates immediately collapses under the weight of corroboration.

On a similar note, Cerling (1990) used the radiocarbon dates from Lake Bonneville shorelines to calibrate another dating technique, which measures the accumulation of 3He to estimate how long certain minerals have been exposed to the surface (useful for dating floods, landslides, eruptions, etc.). Success of this technique, which assumes the accuracy of shoreline dates, further corroborates the big picture of glacial Lake Bonneville.

A young-Earth spin also leaves too little time for the lake to have alternated between salt and freshwater (see below). Lake levels can change catastrophically, but rapid salinification? Not a chance. Most importantly, any young-Earth interpretation must ignore the much longer geological history beneath the salt flats and modern lake (Kowalewska and Cohen, 1998). The recent journey from Lake Bonneville to Great Salt Lake is only one at the end of an ~800,000-year string of similar transitions associated with glacial-interglacial cycles. Lakes and marshes (often saline) of various size and lifespan have covered the region since 2.1 million years ago, and the modern landscape has been in place for ~5 million years. No matter how one twists the timeline, 4,500 years is far too little to explain what represents only a thin slice at the top of the geologic column in northern Utah.

How did the lake become salty?

The Great Salt Lake is perhaps known best for its foul smell to those who frequent its shores, due to the abundance of rotting brine shrimp. These hypersaline inhabitants are the only trace of aquatic life in the lake, whose salinity far exceeds that of the ocean. In a young-Earth scenario, it might sound reasonable to posit Lake Bonneville as a remnant of the receding flood waters, but this hypothesis fails the test of chemistry. The modern salt composition is explained rather by the evaporation of river and spring water flowing into the lake (Spencer et al., 1985). When evaporation exceeds river and rainfall input, the salt content increases, because only calcium carbonate precipitates from the lake in large quantities, despite that numerous ionic compounds are carried in by rivers. In other words, the Great Salt Lake is the final product of more than 10,000 years of freshwater distillation.

Didn't Lake Bonneville drain catastrophically?

To an extent, yes. As Earth began to warm following the peak of the last ice age, a natural dam at the north end of Lake Bonneville failed. Nearly 400 cubic miles of water gushed into southern Idaho through the Snake River valley, carving numerous telltale features of megafloods into the landscape (read the full story here). As a result, Lake Bonneville fell as much as 100 meters in a geological instant.

Scablands and dry falls cut into basalt along the Snake River (image from Digital Geology of Idaho).

On the one hand, Lake Bonneville bears at least one 'monument to catastrophe', but this event puts into perspective the slow and gradual histories that bound it. The water loss during the Bonneville flood represents only half the amount lost over thousands of years of slight flux imbalance. Combine this with the fact that lakes comparable to Bonneville appeared and disappeared multiple times prior to its own existence (and without the aid of catastrophic discharges). The Bonneville flood further illustrates how catastrophic flooding affects the surface of the Earth, carving mega-ripples, pot marks, and waterfalls, to name a few geological oddities characterizing 'scablands'. These features remain 'oddities' precisely because the vast majority of Earth's surface never was subjected to catastrophic flooding.


Want to know more about the Great Salt Lake?

More than a fascinating geological site, the Great Salt Lake has both intrigued and challenged humans over a long and complicated relationship. If you want to know more about 'Our Inland Sea' from a human perspective, I highly recommend the documentary below, which packs a thoughtful arrangement of little-known, sometimes bizarre facts about the lake into 43 minutes. How did Native Americans make use of the 'sea'? The Mormons? What role did the lake play in western tourism and entertainment? You may be surprised...

Visit www.greatsaltlakedvd.com to order a copy, or view the trailer on YouTube. The semi-retro style of the documentary (and host's attire) might invoke some hesitation, but I actually enjoyed these aspects by the end. In my opinion, the video is very informative and entertaining given the modest price, and who knows, it might even inspire an upcoming visit to this natural monument.

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