Composite volcano is also known as stratovolcano and is the more explosive of its kind. It is the resulting formation caused by multiple eruptions where alternating layers of lava, ash, cinders, blocks and rock build up on top of each other. The lava, which gushes from such mountains, is highly viscous and hardens upon cooling without spreading too far. The continuous build adds to the height of the mountain.
Typically these kinds of formations are peaks of elevated height that are predominantly snow capped. They have steep sides and symmetrical cones and reach heights of 8,000 feet. Mountains of this type have a crater formation at their summit, which provides a passageway, to either a central vent or a nexus of vents. The distinctive feature of these mountains is a conduit system. When the molten magna collects in chambers beneath the earth’s surface, the conduit provides it passage to the surface. When lava pours forth, it makes its way through the breaks in the crater or from fissures that are on the flanks. This entire network of underground passages and multiple openings in the earth’s crust make the composite volcano eruptions so dramatic. Such kinds of mountains usually experience long periods of dormancy and then reawaken with full vigor.
Since these mountains tend to experience long periods of quiescence, after eruptions have settled down, erosion starts to set in. This gradual process strips away the cone and the hardened layers of lava are exposed. Over the course of time, even these are subjected to wearing away, and all that remains is the remnant of a once powerful and destructive mountain.
In history, some of the most damaging eruptions have been the result of composite volcanoes exploding and causing immense destruction. Such massive eruptions usually have major climatic impacts. Due to the force of emissions the eruption results in expelling huge ash clouds that tend to be suspended in the atmosphere for long periods. Most often these clouds will shroud the entire earth and result in global cooling of temperatures. Mount Pinatubo’s 1991 eruption was one such an event when temperatures dipped worldwide, and Mount Tambora’s earlier eruption of 1815 was so severe when its volcanic ash cloud created such climatic havoc that the following year of 1916 was termed as “The Year Without A Summer”.
While the eruptions themselves are disastrous enough, the ensuing pyroclastic flows that follow play a prominent part in intensifying the damage done. These flows are deadly hazards that are triggered by volcanic eruptions and being mixtures of hot volcanic debris and toxic gasses, they can add to death and destruction caused by composite volcano eruptions. Mudflows are the other result of such powerful explosions. These flows are mixtures of volcanic residue and water and spread with immense speed. They bury almost everything that comes in their path and can completely destroy the landscape of the affected area.
Well known examples include Mount Fuji inJapan, Mount Etna inItaly, Mount St. Helens inWashington and Mount Pinatubo in theCaribbean. While these mountains have experienced relatively recent periods of activity, some very notable others are known for their historical association. Mount Vesuvius, which was responsible for the complete destruction and burial of the city ofPompeii, was another composite volcano that wreaked complete havoc on its victims.
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