September 19, 2010
Deserts and Glaciers
Deserts cover about one-third of the earth’s surface and have unique geologic features that cannot be found in more humid environments. The features found in deserts are mostly formed by wind and water erosion. Desserts are usually created because they are located in a dry region downwind of a mountain range caused by air losing its moisture as it passes over mountains, also known as a rain shadow. Rocks of different hardness and strength weather at different rates producing many of the unique shaped structures in found in the desert. There are many geological forms found in the desert, but here are a few of the unique ones. Arroyo is a dry gully, usually a small, narrow canyon with steep walls and flat, gravel floor. A butte is a narrow flat topped hill of resistant rock with very steep sides, which may have previously been a mesa. A mesa is a large, flat topped hill with cliffs with a resistant rock layer. A hoodoo has a column or pillar shape and this is caused by differential erosion on rocks of different hardness. Glaciers create landforms by erosion as well. A glacier is a large body of ice that is formed on land from the compaction and recrystallization of snow. Glaciers move slowly downhill due to gravity. The erosion features of a glacier can be extremely large or extremely small. As a glacier moves, its scours away material underneath it pulling up rocks, this is the material that is embedded in the ice at the base of a glacier. Though there are many landforms caused by glaciers but here are a few, cirque, crevasse, erratic, a kettle. A cirque is a bowl shaped depression carved out of a mountain by an alpine glacier. A crevasse is a deep, vertical crack that develops in the upper portion of glacier ice. Erratic is a large boulder that a glacier deposits on a surface made of different rock. And a kettle is a shallow, bowl shaped depression formed...