Volcanic activity

This animation demonstrates different types of volcanic eruptions.

Geography

Keywords

volcano, magmatic activity, volcanic eruption, volcanoes, volcanic activity, magma, post-volcanic activity, magma chamber, plate tectonics, earthquake, lava, mountain formation, Mount Vesuvius, nature, geography, tectonic plate, Earth's crust, disaster

Related items

Scenes

Mt. St. Helens
Mt. Pelée

- An opening in the Earth's crust emitting sulfurous gases.

Mt. St. Helens
Mt. Pelée

Narration

Volcanic activity is a process of magma being ejected to the surface of the Earth out of its crust. Volcanoes do not occur at random; they form long chains, which are essentially the boundaries of tectonic plates.
Volcanic activity has an important role in mountain formation. Magma is red-hot, molten rock beneath the Earth's surface. Magma that flows to the surface is called lava, and a volcano is formed where it reaches the surface. Volcanoes can be differentiated according to types of eruption, which are explosive, effusive and mixed.

Explosive eruptions are characteristic of cinder cone volcanoes. This type of eruption is accompanied by steam and gases that escape to the surface through the crater with massive explosions, and it results in a tall eruption column and pyroclastic flow. Wind can spread the ash cloud over a large area. The pyroclastic flow rolls down the volcanic cone at a high speed. It is the most devastating type of volcanic eruption. Krakatoa, Mt. Pelée and Mt. St. Helens are the best-known examples of volcanoes where this type of eruption occurs.

Effusive eruptions are characteristic of shield volcanoes. This type of eruption is not accompanied by explosions or a pyroclastic flow; the only substance that rises to the surface is liquid lava. Once the lava solidifies, it creates a volcanic cone. Examples of volcanoes where effusive eruptions occur are Mauna Kea and Mauna Loa, both on the Hawaiian Islands.

Mixed eruptions are characteristic of stratovolcanoes. This type of eruption is accompanied by explosions and lava flows as well. The volcanic cone consists of alternating layers of tephra, or fragments, and solidified lava. The best-known examples of stratovolcanoes are Stromboli, Mt. Etna and Cotopaxi.

After volcanic eruptions, postvolcanic activity can also be observed, which essentially consists of steam and gases made up of various chemicals emitted from vents called fumaroles.

A solfatara is a type of fumarole; it is an opening in the Earth's crust that emits sulfurous gases.

A mofetta is a discharge of carbon dioxide. A mofetta can be called 'dry' if it contains carbon dioxide or 'wet', if it contains carbonated water.

A geyser is a spring that periodically discharges hot water. This happens because water seeps into and accumulates in small hollows beneath the ground and then starts to boil due to the heat of the magma, and eventually erupts.

Volcanic activity in clay areas are accompanied by 'mud volcanoes', where gases are released by liquid mud as bubbles.

The most devastating volcanic eruptions scatter large amounts of tephra.
During the 1883 eruption of Krakatoa, 18 cubic kilometers (4.32 cubic miles) of tephra were dispersed, while during the 1815 eruption of Mount Tambora, which was one of the most powerful eruptions in history, a total of 80 cubic kilometers (19.19 cubic miles) of these fragments were spread over a large area.
Such powerful eruptions have global impacts on the Earth's atmosphere, climate and wildlife as well.

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Volcanic activity