Eruption. Main classification
Volcanoes are called uplands, separatelyThey are above the channels and cracks in the earth's crust, through which the products of the eruption are removed from the deep magmatic foci. They have the shape of a cone with a crater on top. The mouth of the volcano is a channel that connects the hearth to the surface of the earth.
Products that are delivered to the terrestrialsurface, differ in volume and composition. In addition, the eruption of the volcano can occur with varying intensity and duration. With these characteristics in mind, the most common classification of activity types is compiled. It should be noted that one volcanic eruption can take one or another character.
The Plinian type is named after Pliny the Elder. The Roman scientist died at the eruption of the volcano Vesuvius in 79 AD. e. The Plinian type is very intense. The eruption of the volcano is accompanied by the release of a large volume of ash to a height of about twenty to fifty kilometers and can last several hours or sometimes even days. Emission products spread over a large area, and their volume ranges from 0.1 to 50 and more cubic kilometers. The eruption of the volcano in the Plinian type can result in the collapse of the hill and the formation of the caldera. In some cases, scorching clouds are formed, but lava flows do not always occur. According to this type, the volcano St. Helens (in the USA) erupted in 1980.
Peleic type is characterized by the presence of a viscouslava. It hardens to the exit, while forming one or more extrusive domes. Thus erupted the volcano Montagne Pele (on the island of Martinique) in 1902.
Vulcan type is shortactivity. Eruptions can last for several minutes or hours. However, they resume within a few months after a few days or weeks. Eruptions of this type are characterized by the presence of flowing magma, the formation of lava flows. The structures are formed from pyroclastic material and lava. The volume of such stratovolcano ranges from ten to one hundred cubic kilometers. Extrusion dome and ash emissions are not always noted. Vulcan type erupts in Guatemala Fuego volcano.
The Strombolian species is called so in honor ofthe Mediterranean island of Stromboli. This type of eruption is characterized by continuous eruptive activity for several months (sometimes even years). At the same time, the eruptive pillar rarely rises above ten kilometers. Some eruptions form slag cones. They consist of basaltic (predominantly) or andesite (rarely) slag. Cones, as a rule, are formed with one eruption, and volcanoes themselves are called monogenic.
Hawaiian-type emissions are characterized byoutput of liquid lava. Fountains from faults and cracks can reach one, sometimes two thousand meters in height. When there is only one muzzle, the lava diverges radially. In this case, shield elevations are formed with very gentle slopes (up to ten degrees). Such elevations are layered and do not contain ash. Shchitov is the largest volcano in the world of Manua-Loa (in Hawaii). Its height is 4103 meters. This eminence has a length of one hundred and twenty, and a width of fifty kilometers. The streams of its lava spread on the island over an area of more than five thousand square kilometers. Of the forty two and a half thousand cubic kilometers, the volume of more than eighty percent is below sea level.
There are other types of eruptions. However, they are extremely rare. So, for example, as a result of an underwater eruption in 1965 in Iceland the volcano Surtsey formed an island.