Thursday, June 24, 2010

Canyon Carved in Three Days

There is an interesting article in the June 20 issue of Nature Geoscience.

Rapid formation of a modern bedrock canyon by a single flood event
Michael P. Lamb & Mark A. Fonstad
Published online: 20 June 2010 | doi:10.1038/ngeo894
River canyons are thought to be cut slowly over millions of years. However, at Lake Canyon Gorge, Texas, a seven-metre-deep canyon was cut in just three days in 2002, providing insight into the erosion processes operating during megaflood events.

Here is a link to a press release on the Caltech web site that summarizes their findings: "Caltech Geologist Investigates Canyon Carved in Just Three Days in Texas Flood"
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.

According to a new analysis of the flood and its aftermath—performed by Michael Lamb, assistant professor of geology at the California Institute of Technology (Caltech), and Mark Fonstad of Texas State University—the canyon formed in just three days.
A waterfall, now dry, formed during the 2002 flood.
[Credit: Michael Lamb/Caltech]

Eroded gorge.
[Credit: Michael Lamb/Caltech]

The scientists' research is focused on gaining better understanding into how canyons are formed, with the hope that they will get insight into canyon formation on Mars. This is quite a unique situation in that scientists were able to witness a geological event in real-time.

Of course, the immediate question in my mind was, "Well, if this canyon can form in three days, why couldn't the Grand Canyon have formed in a few months about 5000 years ago in a global flood?" Seems possible, right? I have to admit, this seems like some pretty compelling evidence on the surface.

Well...not so fast. It's only under certain conditions where a mini-canyon can form this quickly. More importantly, you can't form both rocks AND a canyon simultaneously.

Dr. Jeff Zweerink at Reasons To Believe briefly discusses this research in a recent podcast. I wish he spent more time on the global flood issue, but he does touch on it. (The discussion about young-earth flood geology starts about half-way through.) Mostly, he just talks about the research itself.

Events like this will help to refine our understanding of flood models, which is actually pretty cool.

UPDATE (7/6/2010): I interviewed geologist and Grand Canyon specialist, Carol Hill, about this research and whether or not it provides a good analogy for global flood geology.

"Interview with Geologist, Carol Hill"

1 comment:

Virginia Peterson said...

I finally got around to listening to Jeff's podcast today, and had a couple comments. First, the Grand Canyon is not all made of hard rocks like basalt, granite and gneiss, which was the impression he gave. Those are just the rocks at the bottom. The rest of the canyon has pretty much about every kind of rock you could have, such as sandstone, limestone, conglomerate, shale, etc. The differences in hardness and therefore erosion rates of the rocks are why the canyon is shaped the way it is, with cliffs and terraces. Also I've heard that it's not just the Colorado River that cuts the canyon - a lot of
erosion occurs when there's a rainstorm that sends water down side streams and over the edge. Also there are the effects that freezing and thawing have
in loosening rocks.

In any event, there's still a lot of discussion about how Grand Canyon was actually formed and how long it took. One book is "Carving Grand Canyon: evidence, theories and mysteries" by Wayne Ranney.