[고등 영어 기말 대비] 금성 김[5과] wonders of weathering 좌지문 우해석
5과 좌지문 우해석.hwp
Wonders of Weathering
Limestone is found everywhere on Earth. These areas are very sensitive to weathering, which may create a specific landscape called a karst. Karsts are unique landscapes formed by the underground erosion of limestone by water. Karsts are formed over a long period of time, and they offer a great wealth of scientific and educational opportunities. Underground karst environments, in particular, can provide a relatively undisturbed window into landform evolution and past environmental conditions.
For a limestone landscape to develop into a karst landscape, several conditions are necessary. Calcium carbonate must comprise at least 80% of the rock. The rock must also contain pockets of air, and have a cover of thick vegetation. In karst landscapes weathering is concentrated along the joints and bedding planes of the limestone, producing a number of different features. Rainwater made acidic by carbon dioxide in the atmosphere and soil slowly makes its way into cracks in the limestone, dissolving the rock. As with all weathering processes, time is a factor. Early in the 20th century, karst landscapes were understood to progress through evolutionary stages of development, as if they were aging. But today these landscapes are thought to be locally unique, a result of specific conditions. Mature karst landscapes do display certain characteristic forms.