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. |
This valley is one that was greatly modified by glaciers during the last ice age. A valley glacier commonly fills more than half of the valley length, and as it moves, it modifies the former V-shaped stream valley into a broad U-shaped or trough-like form. The head of the valley is sculptured into a large amphitheater called a cirque (visible in the middle background). Where several cirques approach a summit from different directions, a sharp, pyramid-shaped peak called a horn is formed (middle background). The projecting ridges and divides between glacial valleys are subjected to rigorous ice wedging, abrasion, and mass movement. A knife-edged ridge (arete) is the result of glaciers coming together from opposite directions (from left to middle of photo) Moraine material composed of rock fragments is created from glacial erosion. A truncated spur is visible on the right side of the photo just above the tree-covered ridge 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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