|Craters on Mount Cameroon|
|The volcanic crater of a Tangkuban Parahu |
mount, West Java, Indonesia
Breached craters have a much lower rim on one side than the rest. A crater may be breached during an eruption, either by explosions or by lava, or through later erosion.
Some volcanoes, such as maars, consist of a crater alone, with scarcely any mountain at all. These volcanic explosion craters are formed when magma rises through water-saturated rocks and causes a phreatic eruption. Volcanic craters from phreatic eruptions often occur on plains away from other obvious volcanoes. Not all volcanoes leave craters.