Word: lavas
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...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 become massive...
...Mount Skaptar erupted in Iceland, filling a valley with lava up to 75 ft. deep. The blast's devastating effects on farming and fishing caused a famine that killed 10,000 (one-fifth of the country's population) and destroyed most of the island's livestock...
...Mount Katmai, in Alaska's remote Aleutian Range, belched a 15-mile flood of lava. There were no known fatalities, but it was the largest blast in North American history-ten times the magnitude of the one at Mount St. Helens...
...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 and ashes. The mountain literally blows its top. Eruptions may also occur where the plates tear apart. One such place...
Though volcanoes can kill - eruptions have cost more than 100,000 lives in the past two centuries - they have a kindlier side as well. Some of the world's most fertile soil, like that on the Indonesian island of Java, has been created by lava and ash from volcanoes. The crystalline material, mostly silicates, is often rich ash only calcium and a variety of other elements. The lava and ash not only help the soil retain moisture but they weather rapidly and usually release valuable nutrients. Volcanic debris can also be used commercially as cement additives, as ingredients...