Volcano

The Volcano

The very mention of the word “volcano” conjures up images of a fiery and angry Earth releasing molten lava and rock into an otherwise peaceful world – a violent speck on a serene landscape. Indeed, many of the world’s volcanoes lie in some of the most pastoral landscapes on the planet: forest-filled mountains, blue sea coasts, and on tropical islands. How these were all formed, however, have everything to do with the disruption and sudden change that a volcano eruption brings.

In essence a volcano is simply nothing more than a rip, puncture, or otherwise natural opening in the crust of our planet. Most islands and mountains were formed with the hot volcanic rock that was spewed out of tension-filled volcanic eruptions from deep within the Earth. While volcanoes can – and do – form just about everywhere, they are most commonly found where the various plates that make up the crust of our planet meet. The Pacific Plate is one of the biggest of these – also known as tectonic plates. The Pacific tectonic plate extends along most of the western shore of North America, around the northern and southern sides of the Pacific Ocean, and along the east coast of Japan. The lines where these converging of plates occurs, for example, is known as “the Ring of Fire” – an active ring of volcanic and seismic (earthquake) activity that reflects the ever- changing force of the world below us.

Volcanoes are also formed when two tectonic plates diverge, or pull away, from one another. While convergent tectonic plates usually occur along the land, the divergent plates are more commonly found deep underwater; the Atlantic Sea is known for its constant volcanic activity from these types of plates. Underwater layers and crusts are built up, or ridges are formed when underwater volcanoes erupt. Other times, the eruptions are so large that entire islands can be formed – such was the case for Iceland. The final cause of formation for a volcano is in “hot spots” – these are areas where the crust of the earth is especially thin, allowing for the melting of the crust via mantle plumes.

These mantle plumes occur when the hot rock deep inside the core of the Earth is pressurized to the surface. With both types of tectonic plate volcanic formations, a magma chamber is formed beneath the surface of the Earth and then swells up to the crust. In both instances, a pipe is formed, which is also known as a conduit. This conduit allows the magma and hot rock to vent from the Earth’s core to the surface, releasing pressure. The conduit widens at the throat of the volcano, which is near the top of the visible eruption point at the crater. The crater, along with the dome of the volcano itself, can vary in size due to factors including age of the volcano and frequency of eruptions – all of which help to build layers of ash and lava around the conduit. Over time, these layers can grow so large that they can form mountains – California’s Mount Shasta and Washington’s Mount St. Helens are just two such examples. When volcanoes are built in this method with the alternating layers of cinder, ash, and lava, they are known as stratovolcanoes (or composite volcanoes). Other types of cones, known as cinder cones, lack the heavy build up of ash and lava characteristic of more traditional volcanoes and usually do not remain active past their initial eruption; Arizona’s Sunset Crater is a good example of this.

A handful of volcanoes have been classified as supervolcanoes – these volcanoes are so large that they were not known about for centuries; entire towns and cities have been built inside of them in some cases, with residents completely unaware that they were living inside such a structure. Only two of these exist in The United States – the Valles Caldera in New Mexico and the Yellowstone Caldera in Wyoming. While considered active volcanoes, their last eruptions were 60,000 and 640,000 years ago, respectively.

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