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Volcanoes - THE THIRD PLANET VOLCANOES Introduction Eric R...

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THE THIRD PLANET Eric. R. Swanson – spring 2009 VOLCANOES Introduction If your grade school teacher taught you anything about geology it may well have been that a volcano consists of a mountain with fire and smoke coming out of the top. Unfortunately your grade school teacher had it wrong and now is the time to put bury the smoking mountain theory along with any thought that diamonds are made by Superman squeezing coal and that the moon is made of green cheese. A volcano, it turns out, has nothing to do with fire or smoke and it may not even be a mountain. A volcano is a vent through which molten rock arrives at the surface . Molten rock, or magma as it is called, is hot enough to be incandescent. Erupting magma glows in the dark and so the confusion with fire. Igneous rocks, however, will not burn. An hour or two spent trying to light a block of basalt should be enough to convince even the most dedicated fans of the smoking mountain theory. Rocks will melt and glow just as hot steel does. Magma arrives at the surface and is erupted through an opening called a vent, but magma is typically not just molten rock. Most magma has already started to solidify by the time they reach earth’s surface and so have had time to crystallize at least a few solid mineral grains. Magma also contains dissolved gas, much like the carbon dioxide gas dissolved in soft drinks. Pulling the top off of a soda relieves the pressure and causes the gas to bubble out. The same thing happens when magma rises to clear the vent of the solidified magma from the last eruption. Magma bubbles burst and rise upward as very small chunks and slivers of rock that resembles smoke, but volcanic clouds are not the result of burning and they contain bits of solid rock and not particles of soot. Without gas, the volcano would not erupt. So the following is some of what should be taught in grade school: VOLCANOES: YOU DON'T WANT ONE IN YOUR YARD by Dr. I.M.A. Picklehead Ph.D. Let's learn about volcanoes, It isn't really hard. You probably know already You don't want one in your yard. But do volcanoes flame, as some folks claim, Or puff smoke in addition? Are they always cratered mountain tops, What is their definition? A fiery, smoking mountain So the story usually goes. But there really is no fire, Only molten rock that glows. 1
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THE THIRD PLANET Eric. R. Swanson – spring 2009 And that "smoke" is specks of molten rock That's blown to bits by gas. It just seems to billow up like smoke, And fall to earth as ash. A volcano's just a place from out which Molten rock is sent. An opening at Earth’s surface, Through which ash and lava vent. Volcanic Rocks Volcanic rocks can be classified into three main types based upon the rock’s composition. Basalt is a dark, heavy rock that is relatively rich in heavy elements like iron and magnesium and relatively low in silicon. Rhyolite is compositionally at the other end of the spectrum. Rhyolite is so high in silica that there is not room for other elements much else. It is light in weight and generally light in color.
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