Avolcanic crater is an approximately circular depression in the ground caused byvolcanic activity.[1] It is typically a bowl-shaped feature containing one or more vents. Duringvolcanic eruptions, moltenmagma andvolcanic gases rise from an undergroundmagma chamber, through a conduit, until they reach the crater's vent, from where the gases escape into the atmosphere and the magma is erupted aslava. A volcanic crater can be of large dimensions and sometimes of great depth. During certain types ofexplosive eruptions, a volcano's magma chamber may empty enough for an area above it to subside, forming a type of larger depression known as acaldera.
In most volcanoes, the crater is situated at the top of a mountain formed from the erupted volcanic deposits such aslava flows andtephra. Volcanoes that terminate in such asummit crater are usually of a conical form. Other volcanic craters may be found on the flanks of volcanoes, and these are commonly referred to asflank craters. Some volcanic craters may fill either fully or partially with rain and/or melted snow, forming acrater lake.[2] These lakes may becomesoda lakes, many of which are associated with active tectonic and volcanic zones.[3]
A crater may be breached during an eruption, either by explosions or bylava, or through later erosion. Breached craters have a much lower rim on one side.
Some volcanoes, such asmaars, consist of a crater alone, with scarcely any mountain at all. These volcanic explosion craters are formed when magma rises through water-saturated rocks, which causes aphreatic eruption. Volcanic craters from phreatic eruptions often occur on plains away from other obvious volcanoes. Not all volcanoes form craters.
^Kempe, Stephan; Kazmierczak, Józef (January 2011a)."Soda Lakes". In Joachim Reitner and Volker Thiel (ed.).Encyclopedia of Geobiology. pp. 824–829.doi:10.1007/978-1-4020-9212-1_192.
