A
volcanic crater is a roughly circular depression in the ground caused by volcanic activity. It is typically a bowl-shaped feature within which occurs a vent or vents. During volcanic eruptions, molten
magma and
volcanic gases rise from an underground
magma chamber, through a tube-shaped conduit, until they reach the crater's vent, from where the gases escape into the atmosphere and the magma is erupted as
lava. A volcanic crater can be of large dimensions, and sometimes of great depth. During certain types of
explosive eruptions, a volcano's magma chamber may empty enough for an area above it to subside, forming a type of larger crater known as a
caldera.