Topics: Volcano, Lava, Volcanology Pages: 4 (1413 words) Published: March 7, 2011
A volcano is simply defined as an opening in the earth's surface crust through which molten lava, ash, and gases are ejected.Volcanoes occur most often on or near crustal plates or boundaries, although certain volcanoes known as hotspot volcanoes can occur virtually anywhere,So today Im going to be talking about the different types of volcanoes and what it really means. Volcanoes all generally fit into one of six different categories: Shield volcanoes, Cinder volcanoes, Stratovolcanoes, Submarine volcanoes, Subglacial volcanoes, and the most powerful volcano of all, the Super volcano. What Happens when a volcano erupts?

Lava can flow slowly or erupt violently into the air. The rocks blown out of a volcano – called pyroclastic rock – fall back to earth as dust, ash, cinder or pumice. Most volcanic ash falls to the ground; cemented together by water it forms a rock called volcanic tuff. Depending on how often they erupt, volcanoes may be classified as active, intermittent, dormant, or extinct. Pyroclastic Flows — mixtures of hot gas, ash and other volcanic rocks which travel very quickly down the slope of a volcano. The heat is so great that anyone caught in such a flow will most likely be killed. The speed of the pyroclastic flow is so fast that it cannot be outrun and it is best to evacuate all people living near a volcano that is suspected of producing this kind of flow. Nues Ardentes — literally, "incandescent cloud." One of the most destructive kinds of volcanic eruptions, it occurs when viscous magma erupts under reasonably low pressure, causing a glowing cloud of ash and pumice to be thrown into the air. This mass avalanches back to earth before it can cool off. Made up of a mixture of gas, lava, blocks, ash and pumice, nues ardentes can reach speeds up to 310 mi/hr (500 km/hr). Volcanic Ashes — volcanic rock which is exploded from a vent in fragments less than an inch (2.5 cm) in size. Volcanic ash particles are like small sharp glass particles that damage...
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