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Hilina Slump
The Hilina Slump is a 5,000 cubic mile (20,000 kilometre³) section of the Big Island of Hawaii on the south flank of the Kilauea volcano. Between 1990 and 1993, Global Positioning System measurements showed a southward displacement of the south flank of Kilauea up to approximately 10 centimeters per year. The slump has the potential of breaking away at a faster pace in the form of an underwater landslide. In Hawaii, landslides of this nature are called debris avalanches. If the entire Hilina Slump were to slide into the ocean at once, it could cause an earthquake in excess of a 9 in magnitude, and a megatsunami. Previous megatsunamis in Hawaii 110,000 years ago caused by similar geological phenomena created waves 1,600 feet (500 m) tall.〔(Britt, Robert Roy ), "The Megatsunami: Possible Modern Threat", ''Live Science'', 14 December 2004.〕 Were such a megatsunami to occur again, it would threaten the entire Pacific Rim.
==Geology==
The Hilina slump is sliding seaward on top of the southern flank of the Kilauea volcano, at an average speed of 10cm/year. Kilauea is the southeastern portion, about 13.7%, of the Big Island of Hawaii. Compared to the 25,000 to 35,000 km3 volume of Kilauea, the submarine slide is between 10,000 to 12,000 km3, making up about 10% of the island. Model results based on present day slope and sea level suggest that earthquake accelerations stronger than about 0.4 to 0.6 ''g'' are enough to exceed the static friction coefficient resulting in a slip along a failure surface. However, recent undersea measurements show that an undersea "bench" has formed a buttress at the forefront of the Hilina Slump, and "this buttress may tend to reduce the likelihood of future catastrophic detachment."〔(Hawaiian Landslides ) —Slope failure on Kilauea's submarine south flank (Subsection)〕
As the Pacific plate is being pushed to the west/northwest, it is traveling over a hot spot that is erupting silica poor basaltic magma. The Big Island of Hawaii is the youngest of the chain of Hawaiian shield volcanoes that have penetrated and scarred the overriding Pacific plate. Located on the eastern side of the Big Island, Kilauea and Mauna Loa are believed to be the only Hawaiian volcanoes still being fed on a large scale by the magma chambers below. Since the northeastern flank of the Hilina slump is still growing, the sliding southern flank of the slump may be experiencing friction resisting slope failure as the northeastern flank is pushing upwards. Once the northeast flank becomes inactive, and the resisting frictional force decreases, the Hilina slump may be more susceptible to submarine landslides caused by earthquakes.〔
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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