Volcanoes Essay

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Volcanoes

Distribution Volcanoes can be described as being tectonic hazards that occur in many parts of the world. The distribution of volcanoes is closely linked with the positioning of the tectonic plate boundaries across the globe. Today there are about 500 active volcanoes in the world. The world map of volcanoes in your atlas shows that the most volcanic activity occurs along the West coasts of North and South America, (along the Rockies and Andes) and the coasts of many Far East countries (in areas like Japan, China etc).

The positioning of these volcanoes coincide with major plate boundaries. E.g. the volcanoes along the West coast of North America are the result of the Juan de Fuca
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The pyroclastic flows are clouds of ash, stones etc that move down the side of volcanoes and carry any debris in its way. A famous pyroclastic flow occurred when Mt Pinatubo erupted in 1991. Mud volcanoes, which may form where hot water mixes with mud and surface deposits. Solfataras, that are created when mainly sulphurous gases escape onto the surface. Geysers, occuring when water in the lower crust is heated by rocks and turns to steam, pressure increases and the steam and water explode onto the surface. Fumaroles, formed when superheated water turns to steam as its pressure drops when it emerges from the ground. Formation: - there are three main ways in which volcanoes can be formed.

At constructive plate margins This is where two tectonic plates are diverging away from each other, which causes new crust to be created at the boundary between these two plates. A well known example is where the North and South American plates are pulled away from the Eurasian and African plates due to convection currents. This has caused the formation of the Mid-Atlantic ridge.

When two plates diverge, initially, a rift valley may occur. Magma rises from the mantle filling in the gaps between the two plates, which can cause submarine volcanoes to occur, (volcanoes under water). These volcanoes may rise above sea level thus forming islands. Two examples of this are the island of

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