2015개정 영어1 YBM(한) 6과 본문

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Why Sinkholes Open Up Florida Sinkhole Swallowed a Sleeping Man When Jeff Bush, a 37-year-old Florida man, screamed out for help, his brother Jeremy ran into Jeff’s bedroom. Seeing that Jeff and all his furnishings had vanished into the earth, Jeremy desperately tried to rescue him. He didn’t stop until the police arrived. “I tried so hard. I tried everything I could, but I couldn’t get him out,” Jeremy cried. It was a sinkhole that instantly pulled Jeff into the earth. A sinkhole is a hole that opens up in the ground, which is caused by a collapse of the lands urface. Sinkholes vary in size from 1 to 600 meters deep. Some sinkholes are large enough to swallow entire buildings. Sinkholes have been around for a long time. It is said that the ancient Maya believed sinkholes were passageways to the world of the dead. Unlike the sinkhole in Florida, not all sinkholes are dangerous, destructive, and ruinous. Some sinkholes attract tourists who are interested in the mystery and the beauty of nature. Some notable sinkholes include Sima Humboldt in Venezuela, which is 314 meters deep and Xiaozhai Tiankeng in China, 662 meters deep and 626 meters wide. Sinkholes can form underwater, too. Underwater sinkholes are called blue holes. The Great Blue Hole in Belize is one of the most spectacular; it is300 meters wide and 124 meters deep. Sinkholes typically occur in areas where the rock beneath the surface soil is limestone, carbonate rock, sandstone, or some other soft rock that is easily worn away by water. These kinds of rocks are found in many parts of Florida, Texas, and Kentucky in the U.S. They are also common in the U.K., Mexico, Belize, Slovenia, Croatia, and China.

When rainwater seeps down through surface soil, it eventually reaches the bedrock below. Slowly and continually, sometimes over hundreds or thousands of years, the water erodes small parts of the rock, creating cracks underground. As the process continues, the soil above is gradually washed into the cracks, and it creates a space in the soil. It is not seen on the surface. As the space becomes too large to support the soil above, it collapses, and a hole opens up on the surface. Though sinkholes form gradually, the final collapse of the surface happens suddenly. The most common factor that triggers a collapse is a change in underground water levels. For example, during long periods of drought, underground water levels will fall. When this happens, the space that was once supported by the water may become weaker and collapse. Another trigger is a rapid increase in surface water. A sudden heavy rain can add dramatically to the weight of the surface soil, making it too heavy for the space beneath to bear. This, too, can bring about a collapse. Sometimes the trigger can be man-made. Most sinkholes we are seeing these days are indirectly related to human activities, such as drilling, mining, or construction. They may also occur because of broken water pipes, heavy weight on soft soil, and the removal of groundwater. Collapses from these man-made causes can have especially dramatic effects because they often occur in the middle of a street or in housing areas. Recently, many sinkholes have opened up in urban areas around the world, sometimes resulting in tragic accidents. In 2010, in Guatemala City, an area approximately 20 meters wide and 30meters deep collapsed, swallowing a three story factory and killing 15 people. The sinkhole was caused by the increase of surface water due to tropical storm Agatha and leakage from a local waste water pipe.

Generally speaking, naturally occurring sinkholes cannot be prevented. However, if you live in anarea where sinkholes have happened before, look around for possible warnings, such as leaning trees, doors or windows that don’t close properly, or rainwater collecting in unusual spots. Sinkholes caused by human carelessness can often be prevented. Thorough soil testing prior to construction and maintaining the underground water and plumbing systems are the best ways to prevent the formation of a sinkhole in the middle of a city. Sinkholes are not widespread events like hurricanes or earthquakes. They are very localized. However, this does not mean that we should ignore the possibility of sinkholes. As our population grows and we develop in areas where sinkholes are common, we seem to be seeing more sinkholes and more stories about humans being affected by them. If we look for ways to detect and prevent sinkholes, it may be easier to rescue another Jeff from a sinkhole somewhere else in the world.