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26 June 2010

Secular Geology Admits to Rapid Canyon Formation by Megafloods

June 21, 2010 — It’s hard to deny catastrophic canyon formation when you have the evidence right in front of you. Look what happened in Texas a few years ago, as reported by PhysOrg:
In the summer of 2002, a week of heavy rains in Central Texas caused Canyon Lake – the reservoir of the Canyon Dam – to flood over its spillway and down the Guadalupe River Valley in a planned diversion to save the dam from catastrophic failure. The flood, which continued for six weeks, stripped the valley of mesquite, oak trees, and soil; destroyed a bridge; and plucked meter-wide boulders from the ground. And, in a remarkable demonstration of the power of raging waters, the flood excavated a 2.2-kilometer-long, 7-meter-deep canyon in the bedrock.
The actual canyon was formed in just three days, said Science Daily. Live Science also reported the story, saying, “Some of the most spectacular canyons on Earth and Mars were probably formed in the geologic blink of an eye, suggests a new study that found clues to their formation deep in the heart of Texas.”
Such catastrophic floods and canyons that resulted are not unknown in historic times, but what’s new is that geologists are taking note and applying the lesson of Canyon Lake to large, prehistoric megafloods on earth and even Mars. PhysOrg continued, “Our traditional view of deep river canyons, such as the Grand Canyon, is that they are carved slowly, as the regular flow and occasionally moderate rushing of rivers erodes rock over periods of millions of years.” Quoting Michael Lamb of Caltech, co-author of a paper in Nature Geoscience,1 the article said that such is not always the case: “We know that some big canyons have been cut by large catastrophic flood events during Earth’s history.”
Lamb went on to explain that there is not often an easy way to tell a catastrophically-formed canyon from a gradually-formed one:
Unfortunately, these catastrophic megafloods – which also may have chiseled out spectacular canyons on Mars—generally leave few telltale signs to distinguish them from slower events. “There are very few modern examples of megafloods,” Lamb says, “and these events are not normally witnessed, so the process by which such erosion happens is not well understood.” Nevertheless, he adds, “the evidence that is left behind, like boulders and streamlined sediment islands, suggests the presence of fast water”—although it reveals nothing about the time frame over which the water flowed.
Lamb found that process like “plucking” – in which boulders popped up from fractured bedrock became sledgehammers in the current, and headward-eroding waterfalls, led to quick downward erosion of the canyon. He hopes the features witnessed in the Canyon Lake flood will aid in interpreting megaflood evidence on earth and Mars. Here is the abstract from the paper by Lamb and Fonstad:
Deep river canyons are thought to form slowly over geological time (see, for example, ref. 1 [Grand Canyon]), cut by moderate flows that reoccur every few years 2, 3. In contrast, some of the most spectacular canyons on Earth and Mars were probably carved rapidly during ancient megaflood events 4, 5, 6, 7, 8, 9, 10, 11, 12. Quantification of the flood discharge, duration and erosion mechanics that operated during such events is hampered because we lack modern analogues. Canyon Lake Gorge, Texas, was carved in 2002 during a single catastrophic flood 13. The event offers a rare opportunity to analyse canyon formation and test palaeo-hydraulic-reconstruction techniques under known topographic and hydraulic conditions. Here we use digital topographic models and visible/near-infrared aerial images from before and after the flood, discharge measured during the event, field measurements and sediment-transport modelling to show that the flood moved metre-sized boulders, excavated ~7 m of limestone and transformed a soil-mantled valley into a bedrock canyon in just ~3 days. We find that canyon morphology is strongly dependent on rock type: plucking of limestone blocks produced waterfalls, inner channels and bedrock strath terraces, whereas abrasion of cemented alluvium sculpted walls, plunge pools and streamlined islands. Canyon formation was so rapid that erosion might have been limited by the ability of the flow to transport sediment. We suggest that our results might improve hydraulic reconstructions of similar megafloods on Earth and Mars.
Their references included the paper by J H Bretz on the channeled scablands of Washington, and other research on the Lake Bonneville floods, but no work by creation geologists who have postulated rapid formation of the Grand Canyon by a dam breach megaflood. They did not discuss the Grand Canyon in their paper other than to state in the introduction that “Most bedrock river canyons are thought to be cut slowly over millions of years (for example, Grand Canyon, USA, ref. 1) by moderate flows that reoccur every few years.” They did not say whether they agree with that assessment now in light of their work.
Lamb and Fonstad described in the paper how it is hard to tell slow processes from rapid ones:
It is difficult to identify morphologic features in Canyon Lake Gorge that indicate canyon formation during a 3 day event, versus a longer-lived flood or multiple events. For example, inner channels, knickpoints and terraces are often formed slowly over geologic time in response to shifting climate or tectonic forcing, but in Canyon Lake Gorge and other megafloods they must have formed rapidly through intrinsic instabilities in the erosion processes. A narrow gorge is sometimes inferred to represent slow persistent erosion, whereas Canyon Lake Gorge was formed in a matter of days. It is clear that models for the rate of bedrock erosion are needed to calculate the duration of flooding necessary to excavate a canyon of known volume. Although notable progress has been made, there are no well tested mechanistic models of bedrock erosion via plucking during megafloods.
They did the best they could to come up with a “semi-empirical theory” of sediment transport capacity to account for the rapid erosion of Canyon Lake Gorge. Apparently it was not the strength of the bedrock that limited erosion, but the ability of the water to pick up and move large blocks: “Thus, it seems plausible that erosion of well-jointed rock by large floods might be extremely rapid, such that canyon formation is limited by the capacity of the flood to transport plucked blocks rather than by the plucking processes itself.” Whether that is the only surprising paradigm shift from this observational example of rapid canyon formation remains to be seen. It may be time to change a lot of western national park interpretive signs.

1. Lamb and Fonstad, “Rapid formation of a modern bedrock canyon by a single flood event,” Nature Geoscience, Published online: 20 June 2010 | doi:10.1038/ngeo894.

What does he mean this is not well understood? If the secular geologists had been reading the creationist journals for decades, which are way ahead of the curve on this topic, they would not be so clueless. The Creation Research Society Quarterly, Journal of Creation and other peer-reviewed journals written by creation scientists, with field research and PhDs, have for years been talking about the power of catastrophic processes to produce the Grand Canyon and other large earth features in just days and weeks by breached dams and other megaflooding processes. This is nothing new, but the secular journals and news media act like it is. It’s nice for the secular crowd, still awaking from their Lyellian slumbers, to catch the groove finally (better late than never), but how about some attribution? Creationist authors of papers on this subject should get together and walk into Lamb’s office with a stack of their papers on catastrophic canyon formation by megafloods, pile them on his desk, and ask, “Where have you been all this time?”

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