Volcanic dust is the residue that remains in the atmosphere after the eruption of a volcano. A volcano is a general term for any opening in the crust of a planet or natural satellite through which gases, lava or magma, and solid fragments are discharged. Volcanoes are typically classified as active, dormant, or extinct (Encarta, 1998). The interior of the earth is composed of an inner solid-iron core surrounded by an iron-rich, liquid outer core. Beyond the core is the mantle, a chemically distinct silica-rich layer that extends to the earth's crust, about 4,100 miles from the center of the earth. The mantle is extremely hot, and convective motions transport this heat to the earth's surface. The surface is composed of a series of large, rigid plates that are continually moving, in some places colliding and in others
separating. Three main types of volcanoes form as a result of the motion of the plates and convection in the mantle(Encarta, 1998).
On the planet Earth, there are approximately 1,500 known to be
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