Composite volcanoes are found on destructive plate margins , where the oceanic crust sinks beneath the continental crust. Composite volcanoes have the following characteristics:. An example of a composite volcano is Mount Pinatubo in the Philippines. Shield volcanoes are found on constructive plate margins , where two plates move away from one another.
Composite volcanoes are fed by a conduit system which taps into a reservoir of magma deep within the Earth. Some of the most famous volcanoes in the world are composite volcanoes. And some of the most devastating eruptions in history came from them.
For example, Mount St. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as cinders around the vent to form a circular or oval cone.
Most cinder cones have a bowl-shaped crater at the summit and rarely rise more than a thousand feet or so above their surroundings. Cinder cones are numerous in western North America as well as throughout other volcanic terrains of the world. Schematic representation of the internal structure of a typical cinder cone. Explosive eruptions caused by gas rapidly expanding and escaping from molten lava formed cinders that fell back around the vent, building up the cone to a height of 1, feet.
The last explosive eruption left a funnel-shaped crater at the top of the cone. After the excess gases had largely dissipated, the molten rock quietly poured out on the surrounding surface of the cone and moved downslope as lava flows. This order of events--eruption, formation of cone and crater, lava flow--is a common sequence in the formation of cinder cones.
S ome of the Earth's grandest mountains are composite volcanoes--sometimes called stratovolcanoes. They are typically steep-sided, symmetrical cones of large dimension built of alternating layers of lava flows, volcanic ash, cinders, blocks, and bombs and may rise as much as 8, feet above their bases. Helens and Mount Rainier in Washington. M ost composite volcanoes have a crater at the summit which contains a central vent or a clustered group of vents. Lavas either flow through breaks in the crater wall or issue from fissures on the flanks of the cone.
Lava, solidified within the fissures, forms dikes that act as ribs which greatly strengthen the cone. T he essential feature of a composite volcano is a conduit system through which magma from a reservoir deep in the Earth's crust rises to the surface. The volcano is built up by the accumulation of material erupted through the conduit and increases in size as lava, cinders, ash, etc. Schematic representation of the internal structue of a typical composite volcano.
Composite volcanoes Composite volcanoes, also known as stratovolcanoes, are found on convergent plate boundaries , where the oceanic crust subducts beneath the continental crust. An example of a composite volcano is Mount Pinatubo in the Philippines. Mauna Loa is a shield volcano. Mauna Loa, on the island of Hawaii, is a shield volcano, but was formed over a hotspot , rather than at a divergent or constructive plate boundary.
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