Volcanic crater

See also: Crater

A volcanic crater is a depression coarsely circular or elliptic which is at the top or sometimes on the sides of a Volcan and formed by the explosion or the collapse of the volcano. It can have variable sizes going from a few meters to several tens kilometer in diameter. Nevertheless, beyond of a size of 1 500 meters, one will speak about Caldeira.

The volcanic craters are formed during an volcanic eruption according to different manières :

the accumulation of volcanic materials (Lava S and Tephra S) around the volcanic chimney can form a circular monticule. When the eruption ceases, the place of exit of materials forms a depression when it filled not of volcanic materials or érosion ;
the various explosions occurring during the ejection of volcanic materials can tear off more or less great parts of walls of the volcano around the volcanic chimney, creating or increasing a cratère ;
an important draining of the magmatic Chambre can cause a depression of the volcano in general giving rise to will caldeiras rather than with craters.

The great majority of the volcanos has one or more craters. Only the volcanos made of domes of lava do not have any when those fill completely of possible craters created at the time of preceding eruptions. Several craters can be encased (as with the Erta Ale) or overlap (as with the Olympus Mons on Mars).

The craters can fill of water and to form Lac S. These lakes are then in general very deep. They can store volcanic gases emitted by the volcano in the deep layers of water as it is the case with the Lac Nyos with the Cameroun. When craters open on the sea, they form bays being able to be used as natural ports.

Volcanic craters also exist on Mars, Venus, Io and the the Moon.

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External bonds

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Volcanic crater

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External bonds

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