Hobbies And Interests
Physical Weathering
Physical or mechanical weathering disintegrates rocks, primarily by the process called abrasion. There are different forms of abrasion, depending on weather conditions. For example, in a desert where there is a large difference between night and daytime temperatures, the outer layers of rocks expand and contract, causing layers to peel off. In cold, mountainous regions, freeze-thaw weathering freezes water in the cracks of rocks and expands them, creating larger crevices when the ice thaws.
Chemical Weathering
Chemical weathering alters the composition of rocks. For example, acidic rain causes the dissolution of rock, particularly ones that dissolve easily, such as pyrite. Chalk and limestone dissolve when rain combines with carbon dioxide in the air. This reacts with the calcium carbonate in these rock types to form calcium bicarbonate. This particular dissolution process speeds up in colder temperatures because cold water holds more carbon dioxide. Oxidation is another chemical process that softens rocks, and biological weathering is caused by acidic chemicals produced by plants and animals.
Erosion
Erosion has several agents. Gravity is one. Gravitational forces pull rocks downward, often helped by other eroding agents, such as ice or water. Usually this action is extremely slow, but occasionally it is a sudden mass movement of rock, called a landslide. Water is a powerful eroding agent. Torrential rain moves soil particles, and rivers wear away the banks. Sea currents, waves and tides erode shorelines and the movement of glaciers creates valleys. Wind is another important agent, particularly in dry, desert areas with little vegetation, where it blows small particles, such as sand and dust, across thousands of miles.