Active Volcanic Craters example essay topic
453 words
Kilauea Hawaii consists of a string of islands, or an archipelago. Kilauea is located on one of these islands, the central Hawaii island. Kilauea is one of the worlds most active volcanic craters. Craters are formed either by the massive collapse of material during volcanic activity, by unusually violent explosions, or later by erosion during dormancy (Comptons). It is situated on the southeastern slope of the great volcanic mountain Mauna Loa. Its elevation is 1111 m (3646 ft.) above sea level. The crater has an area of about 10 sq. km., which forms a great cavity in the side of the mountain. Volcanic activity recently has been restricted to an inner crater called Halemaumau. Halemaumau measures more than 900 m (about 3000 ft.) across and has a depth of about 400 m (about 1300 ft.
). Kilauea has erupted at least once a year since 1952. The volcano spews an average of 525,000 cubic yards of lava a day and by 1995 had added about 500 acres of new land to the island (Encarta 98). By June 1989, it had destroyed the visitors center at the national park, a stretch of Kalpana Highway, and more than 65 houses by 1990. Kilauea is located on a hot spot under the island, and the magma is thought to come from a depth of at least 50 km. below the surface. A hot spot is an area of volcanic activity near the center of two lithospeheric plates.
Normally, lava streams constantly into the floor of the crater from subterranean sources which either cools and hardens, or accumulates until it drains off into other subterranean passages. When greater volcanic activity occurs, the lava is subjected to sudden changes of level, where it may escape from vents on the lower slope toward the sea. Kilauea is classified as a shield volcano. Shield volcanoes have a low, broad profile created b highly fluid basalt flows that spread over wide areas. The fluid basalt usually only builds a cone around seven degrees steep. Over thousands of years though, these cones can reach massive size, which is shown in the Hawaiian Island volcanoes.
The Hawaiian Islands are composed of shield volcanoes, that have been built up from the sea floor. If measured from sea floor level, some of the Hawaiian volcanoes are the worlds largest mountains in terms of both height and volume (Comptons). In the 20th century, major flows occurred in 1920 and 1921, 1950, 1955, 1959, 1965, and 1969. The current eruption cycle, the longest-running in modern Hawaiian history, began on January 3, 1983 (Encarta).
