Copyright Information: All images are in the public domain and available for free. If you use this image, credit NOAA/NGDC, John Lockridge, Longmont, Colorado. |
Potholes result when pebbles borne by streams (in this case an intermittent stream) are trapped in a depression and swirled around by currents. The rotational movement of the sand, gravel, and boulders acts like a drill cutting deeply into solid rock. As the pebbles and cobbles are worn away, continue the drilling into the floor of the stream channel. The pothole shown is about two and a half feet deep. Image Credit: John Lockridge, Longmont, Colorado. The hydrologic system, which includes all possible paths of motion of Earth's near-surface fluids including air and water, is largely responsible for the variety of landforms found on the continents. Heat from the sun evaporates water from oceans, lakes, and streams. Although most of the water returns directly as precipitation to the oceans, some of the water is recipitated over land as rain or snow. If it is precipitated over land, it then begins its journey back to the sea as "runoff." The relentless action of surface runoff, streams, and rivers, glaciers, and waves sculpts the rock into intriguing and bizarre shapes. This set of slides includes examples of wave erosion, wind and water erosion, valley shapes, and glacial rosion. The views are often dramatic. Many were taken at U.S. National Parks and Monuments. |
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