Calderas

A caldera is an enlarged crater at the crest of a volcano. It is an enlarged, basin-shaped depression caused be a very violent eruption that blasts off a large part of the volcano. It can also be filled with water to form a crater lake such as Lake Toba in Sumatra, Indonesia.

A caldera can also be formed when a volcano sinks into the magma chamber after several major eruptions. As the magma is removed faster from the magma chamber then it can be replenished; support for the volcano is greatly decreased. As cracks appear in the rocks above the magma chamber, the volcano collapses into the magma chamber, forming a caldera. An example of a crater lake formed in this way is the Crater Lake in Oregon, the USA.

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