The volcanic crater is the bowl-shaped, often well-like depression, which emerges from the magma in a volcanic or leaked. In a stratovolcano or a central volcano, the crater is often at the top of the volcano. If there are several craters, it is the largest and summit next as the main crater, called the other craters as secondary craters.
In a volcanic eruption not only glutflüssige, but also solid or gaseous substances over the volcano crater released ( volcanism ), when the pressure increases due to the gases due to the high temperature of the viscous magma, because the volcano crater itself cools the lava and gradually to a close the volcanic vents leads. The gases can not escape other than by an eruption.
In the literature a distinction is made according to the mode of origin between several crater types:
- Explosion or collapse crater, called Caldera
- Secondary craters (also called Adventivkrater ) arising on the slopes of a volcano eruption in the tearing of the chimney to the pressurized radial columns
- Umwallungskrater caused by large amounts of subsidized day to loose weight, the ring like a wall accumulates around the crater
Must be distinguished from Maare caused by volcanic steam explosion, so-called phreatomagmatic explosions. Also Tuffringe have a similar origin, such as Hverfjall of Lake Mývatn in Iceland.
A crater is not to be confused with a caldera, since this is a slump structure.
If there is a fissure eruption, regular rows of craters can build up over a more open fissure. Examples include the Laki craters or the Vatnaöldur crater in Iceland or even the La Chaîne des Puys crater row in the Auvergne in France.
La Chaîne des Puys crater row
Volcano on Lanzarote, bordered of solidified ash- covered lava