Word: magma
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Dates: during 1980-1989
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...latest round of activity caught scientists by surprise. Though volcanologists have been able to predict almost to the hour when the volcanoes of the Hawaiian Islands will erupt, Mount St. Helens presents a more difficult problem for would-be prognosticators. The molten rock, or magma, underneath the Washington volcano is a thicker, silica-rich material (unlike the less viscous molten basalt of the Hawaiian chain); more pressure must build up before the hot gases trapped within it are released. Thus the mountain erupts infrequently and violently...
According to their scenario, some of the molten rock from the subterranean cauldron of magma under the mountain will slowly be forced upward, like toothpaste being squeezed out of a tube. It will push through the vents in the "plug" of debris within the volcano's throat and emerge as lava. When it is finally exposed to the air, the lava will harden rapidly; it will probably not have enough volume or velocity to overflow the volcano's rim. Instead, as it solidifies, it will likely form a dome or cap over the vents. Eventually the dome should...
...scientists have a more modern theory. It is generally believed that the giant, continent-size plates forming the earth's outer shell crunch together in certain places, such as along the Ring of Fire. On plate slips under, heats up and begins to melt. This molten material, or magma, is lighter than neighboring and slowly rises, often triggering earth tremors. Eventually the magma may break through the surface as lava. In some cases, like that of Mount St. Helens, the magma remains in pools under the mountain, but still releases enough heat to cause explosive ejections of steam, fumes...
...extremely hard black grains, which laboratory examination revealed to be tiny diamonds. Institute Geochemist Emil Sobotovich explained that the little diamonds could only have been created under extraordinarily high pressures. Such conditions deep within the earth produce diamonds, which are brought to the surface in eruptions of molten magma through kimberlite, or volcanic, pipes. But extreme pressures also occur during high-velocity collisions between celestial objects; uralites, a class of meteorites that presumably have been involved in such deep-space impacts, contain such tiny diamonds. Since no volcanic pipes have been identified in the Tunguska area, Sobotovich concluded that...