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Eroded landscape. Aerial photograph showing rock formations in the semi-desert area of Nevada, USA. Erosion of the grey surface layer by wind and rare rainfalls have exposed red rock. Rubble (black) has been deposited along channels that are rivers during wet periods. Harder ribs in the red rock are seen as parallel stripes. (KEYSTONE/SCIENCE PHOTO LIBRARY/Bernhard Erdmaier) === ===