May 23, 2008 | David F. Coppedge

Geology: Another Catastrophic Rethink

Amphitheater-shaped canyons are common throughout the West – and even on Mars.  Geologists had them pretty well figured out.  Water seeps out the bottom of a wall, weakening the face of a cliff.  Gradually, material collapses and leaves a large alcove that continues to recede headward.  That idea is now questioned by a new theory that says catastrophic flooding produces these canyons suddenly.
    Space.com has a summary of a paper published in Science this week that re-evaluated a classic case, Box Canyon in Idaho.  The new theory is that sudden flooding, perhaps from melting ice sheets to the north, released a torrent of water that cut the canyon at one time.  The article estimated the complete canyon, cut into solid basalt, was eroded in 35 to 160 days at most.  The flood theory explains unusual features, like scour marks on the walls and large boulders sitting out in the middle of nowhere, that were difficult to explain with the old theory.
    An idea of the size of this “megaflood” was given in the article.  Michael Lamb, geomorphologist at UC Berkeley, said, “Imagine forcing a quarter of the flow in the Mississippi through a chute 32 times as narrow and 1,000 times as steep as the Mississippi River channel.”  800 to 2,800 metric tons of water could have blasted through the channel at 22 miles per hour.
    Space.com reported this article because of its implications for Mars research.  If megafloods also formed the amphitheater-shaped canyons on the red planet, perhaps calm water did not exist for long periods – a blow for those hoping life would have time to exist.

Another old-age paradigm has had to shift under new investigation.  These kinds of canyons are very common in the arid southwest, like in the Grand Canyon.  Where did the water come from in the desert?  In the aftermath of a worldwide flood, such phenomena would be expected, but not in a place where geologists feel huge seas of Sahara-like sand ruled for millions of years.
    Access Research Network also reported on this paradigm-shifting theory.

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