The volcanic crater is the bowl-shaped, often shaft-like depression from which the magma of a volcano emerges or has emerged. In the case of a stratovolcano or a central volcano , the crater is often at the top of the volcano. If there are several craters, the largest and closest to the summit is referred to as the main crater , the other craters as secondary craters .
During a volcanic eruption will not only glutflüssige but also solid or gaseous substances over the volcano crater released ( volcanic ) when the pressure from the gases due to the high temperature of the viscous magma rises because the volcanic crater itself, the lava cools and gradually form a closing the volcanic vents leads. The gases cannot escape other than through an eruption .
Types of craters
In the literature, a distinction is made between several types of craters according to the type of formation:
- Explosion or collapse crater, called a caldera
- Side craters (also known as adventitious craters ) that arise on the slopes of a volcano when the eruption vent is torn open at the pressurized radial crevices
- Embankment craters are created by large amounts of loose material extracted from the surface, which is deposited around the crater like a ring wall
A distinction must be made between maars that are created by volcanic steam explosions, so-called phreatomagmatic explosions . Also Tuffringe have a similar origin such as Hverfjall Lake Myvatn in Iceland .
A crater is not to be confused with a caldera , as it is a collapse structure.
Row of craters
If it is a fissure eruption, rows of craters can form over an opening volcanic fissure. Examples would be the Laki crater or the Vatnaöldur crater in Iceland or the La Chaîne des Puys crater series in the Auvergne in France .
Montaña de las Lapas volcanic cone on Lanzarote , surrounded by solidified, ash-covered lava
- Felix Frank: Handbook of the 1350 active volcanoes in the world , Ott Verlag, Thun 2003, ISBN 3-7225-6792-0
- Alfred Rittmann : Volcanoes and their activity . Ferdinand Enke Verlag, Stuttgart 1981, ISBN 3-432-87793-5 .
- Rudolf Hohl (ed.): The history of the development of the earth. With an ABC of geology , Hanau 1999, ISBN 3-7684-6526-8