Canyon Lake Gorge, part 1


As promised yesterday, posting on my field trip to the Canyon Lake Gorge. The trip was part of a class I’m taking, and it was quite a privilege to get a look at this place— a pristine “portal” if you will, directly into the Lower Cretaceous.

First, some backstory about the place. Recent backstory, that is.

The photo above, taken yesterday, April 14, 2007, could not have been taken on the same day five years ago. If the two figures above were standing in the same place then, they would have been encased in limestone. Above them would be the same thin layer of fertile top soil and vegetation that you can see on either side of the photo. So, what happened?

Rain. Lots of rain. During the last week of June, 2002, a low pressure system stalled over the Hill Country, dropping more then the annual average rainfall (34-37 inches) in the space of one week.

The dam itself, at the top right of the photo below, is 224 feet above the stream bed surface and the maximum capacity of the lake is 943 feet, mean sea level. The spillway, at the front of the photo, is 31 feet below the level of the dam. After days of rain, on July 5, 2002, a wall of water more than seven feet high crested the 1,250-foot-wide spillway at a velocity of more than 70,000 cubic feet per second, displacing thousands of cubic yards of bedrock and limestone.


(Photo: Larry Kolvoord AMERICAN-STATESMAN)

The tremendous force of the floodwater carved out a mile-long gorge several hundred yards wide, with a maximum depth of approximately fifty feet, all the way back to the Guadalupe River, laying bare limestone from the early Cretaceous Glen Rose Formation, rock that had not been exposed for more than 65 million years.


(Photo: Google Earth)

Continued in Canyon Lake Gorge, Part 2


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