Superstitious Folding

February 18, 2010

20100218 – Thursday - Superstitious Folding

Photographer: Trent Larson
Summary Authors: Thomas McGuire; Trent Larson

February 2010 Earth Science Picture of the Day Viewer's Choice

People who visit the Phoenix Valley of Arizona are often impressed by the mountain rampart to the east: the Superstition Mountains. They're visible from a distance as a nearly vertical wall of rock approximately 2,000 ft (600 m) in height. According to legend, it's here that Jacob Waltz discovered gold at an undisclosed location which has become known as "The Lost Dutchman Mine". The area is popular with hikers but the Superstitions can prove deadly due to the rugged terrain, the scarcity of water and the desert climate with summer temperatures that can reach 120 degrees F (49 c). The geology of the Superstitions is dominated by a collapsed volcanic caldera. The Salt River, with three picturesque reservoirs, cuts through the mountains. The photo above was taken along Fish Creek, one of the few streams flowing out of the Superstitions that is a dependable water source. Volcanic collapse and crushing pressure far beneath the Earth's surface have deformed rock layers. In some places the layers are broken and offset by geologic faults. In other places, such as here, the layers have bent into tightly reversing (recumbent) folds. Erosion by floods along Fish Creek has polished the rocks to a reflective surface. Photo taken on January 25, 2010.