Earth and Moon

The volcanoes

The volcanoes

One of the most spectacular manifestations of the geological activity of the Earth are, without a doubt, the volcanoes.

There are different types, depending on the way the lava leaves, and they are distributed by specific regions of the planet while, in others, there is not.

Volcanoes are also the only places where we can come into contact with the materials inside the crust or the mantle, so they are of great interest to the sciences.

Volcanic eruptions

A volcano is a fissure in the earth's crust on which a cone of molten and solid matter builds up and is thrown through the chimney from inside the Earth. On top of this cone there is a concave formation called crater. When activity occurs on a volcano it is said to be erupting.

Volcanoes are usually structures composed of fragmented material and lava flows. The lava flows through the chimney, which runs down the sides of the cone, which is formed by successive solidified layers, all inclined towards the outside of the chimney.

The rocky material expelled is between 4 and 200 kilometers deep, where they can reach temperatures above 1000 ° C. Usually the newly emitted lava borders temperatures between 700 ° C and 1200 ° C, depending on its chemical composition.

Rocks that form from the cooling of magma are called igneous rocks. If the cooling took place inside the earth, and the molten rocks did not emerge to the surface, they are called intrusive igneous rocks. When the rock has formed from the cooling of lava on the surface, it is called extrusive igneous rock. There are also igneous rocks cooled to great depth that are called plutonic.

Magma and lava

The magma, thick and viscous mass, is the molten rock that is located in the internal part of the volcano subjected to great pressures, and is constituted by gases that are dissolved, but at the time of reaching the surface, the pressure decreases, which causes its explosive and spontaneous release.

The molten material that is thrown out of the volcano contains less gas and, to differentiate it from magma, it is called lava.

The lava in an eruption is loaded with steam and gases such as carbon dioxide, hydrogen, carbon monoxide and sulfur dioxide. These gases when leaving violently ascend to the atmosphere forming a cloudy cloud that discharges, sometimes, heavy rains.

Lava fragments are classified as bombs, embers and ashes, which are thrown out of the volcano and scattered everywhere. Some large particles fall back into the crater. The speed of the lava depends largely on the slope of the slope of the volcano.

Many volcanoes are born on the seabed, as did the famous Etna and Vesuvius, the islands of Hawaii and many other volcanic islands of the Pacific Ocean.

Huge basins, very similar to craters, are called boilers and are located on the summit of extinct or inactive volcanoes and are occupied by deep lakes. Some boilers formed after cataclysmic explosions that completely destroyed the volcano, or when, after successive eruptions, the empty cone does not support the weight of the walls and sinks.

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Earth's crust faultsTypes of volcanoes