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[Stockbild] Folded rock strata. Aerial photograph of rock strata in an anticlinal (arch-like) fold. Tectonic forces have crumpled the rock upwards to form a mountain. Subsequent erosion has exposed its layered nature. The layers of rock are seen as ridges running along the contours of the eroded mountain. The red areas are approximately 200 million years old. The inner core of older rock (upper right) has been exposed and forms a remnant ridge of Sheep Mountain, Wyoming, USA. (KEYSTONE/SCIENCE PHOTO LIBRARY/BERNHARD EDMAIER) === ===