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References:
Colorado Scientific Society 1997-2004, Vince Matthews
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Geology Surrounding the Creede Area
Did you know that Colorado is one of the premier areas in the world for studying caldera-forming processes?
Caldera-forming eruptions are the largest eruptions on Earth. Calderas form when large ash flows spew out of the earth creating voids that the overlying rocks collapse into (Crater Lake is one example); thus creating circular, or oval, structural depressions. These ash flows came out hot (1,100-1,300°F.), traveled up to 75 miles per hour, and spread as far as 90 miles from their source in Colorado. For example, the Fish Canyon eruption in southwestern Colorado about 28 million years ago erupted more than 5,000 km3 (3,107 miles3) of magma from the La Garita caldera. That is enough magma to bury the entire state of California to a depth of nearly 39 feet.
Colorado has at least nineteen calderas including one of the world’s largest, the La Garita Caldera. It is so large (22 by 47 miles) that for a long time it was hard for geologists to realize that they were mapping in a giant caldera. Several younger, smaller calderas are nested within the La Garita caldera. These include the Bachelor, San Luis, and Creede calderas. The towns of Creede and Silverton both lie within the walls of two of these calderas.
The Creede Caldera was at one time very similar to modern day Crater Lake in Oregon at some point in geologic history however, water in the lake eroded through the rock to form the Rio Grande River of today. This erosion point is now referred to as Wagon Wheel Gap.
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