caldera

As a noun caldera is

caldera.

In vulcanology terms the difference between caldera and bradyseism

is that caldera is a large crater formed by a volcanic explosion or by collapse of the cone of a volcano while bradyseism is a gradual uplift or descent of part of the Earth's surface caused by the filling or emptying of an underground magma chamber and/or hydrothermal activity, particularly in volcanic calderas.