Steven Dutch, Professor Emeritus, Natural and Applied Sciences, University of Wisconsin - Green Bay
Spanish Peaks, Colorado are two peaks that rise abruptly out of the plains east of the Rocky Mountains. East Spanish Peak is 12,683 feet high and West Spanish Peak, shown here, is 13,625 feet high. Although one might assume isolated high peaks like this are volcanoes, they are actually small granite intrusions about 35 million years old. The softer sedimentary rocks around the granite were eroded away, leaving the resistant granite as peaks.
During the ice ages, these mountains were easily high enough to have glaciers. The U-shaped valleys high on the mountain are former glacial valleys. The wall running down the hill at the base of the mountain on the right is a dike. Granite from the intrusions that formed the peaks squeezed into cracks radiating away from the intrusions and hardened. Erosion stripped away the surrounding soft rocks and left the dike standing up as a wall. Hundreds of dikes surround the Spanish Peaks.
West Spanish Peak is located at 37o 22' 37" N 104o 59' 04" W. The view here is looking approximately south-southwest.
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Created 25 November 2005, Last Update 15 January 2020