http://www.msnbc.msn.com/id/37876895...ience-science/

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.

Lake Canyon Gorge, a 23-feet- (7-meter-) deep canyon in Comal County,
Texas, was carved in just three days by a flood in 2002. The flood
scoured a swath of greenery, leaving sand-colored bedrock rubble in
its wake.

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lest creationists get their knickers bunched up, the article goes on
to say:

A single catastrophic flood capable of cutting into bedrock is
extremely rare

The Grand Canyon was formed as the Colorado River slowly wore down the
bedrock. That probably took millions of years though, said geologist
and study co-author Michael Lamb of Caltech in Pasadena, Calif.