Definition: Caldera Depression
Calderas form from the catastrophic eruption of large amounts of felsic lava and ash. Emptying of the magma chamber and subsequent collapse of the overlying volcanic edifice forms a ring-shaped caldera depression up to several kilometers in diameter. The edges of the underlying magma chamber are roughly marked by a ring fracture zone that acts as a conduit for ongoing volcanism and hydrothermal activity.
- A caldera is a large cauldron-like volcanic depression, a type of volcanic crater (from one to dozens of kilometers in diameter), formed by the collapse of an emptied magma chamber. The depression often originates in very big explosive eruptions. The emptying of this magma chamber may also be accomplished more gradually by a series of effusive eruptions from the volcanic system, even kilometers away from the magma chamber itself.