Glossary beginning with C

Volcano Term Definitions


The Spanish word for cauldron, a basin-shaped volcanic depression; by definition, at least a mile in diameter. Such large depressions are typically formed by the subsidence of volcanoes. Crater Lake occupies the best-known caldera in the Cascades.

Capping Stage

Refers to a stage in the evolution of a typical Hawaiian volcano during which alkalic, basalt, and related rocks build a steeply, sloping cap on the main shield of the volcano.

Central Vent

A central vent is an opening at the Earth's surface of a volcanic conduit of cylindrical or pipe-like form.

Central Volcano

A volcano constructed by the ejection of debris and lava flows from a central point, forming a more or less symmetrical volcano.

Cinder Cone

A volcanic cone built entirely of loose fragmented material (pyroclastics.)


A steep-walled horseshoe-shaped recess high on a mountain that is formed by glacial erosion.


The breaking of a mineral along crystallographic planes, that reflects a crystal structure.

Composite Volcano

A steep volcanic cone built by both lava flows and pyroclastic eruptions.

Compound Volcano

A volcano that consists of a complex of two or more vents, or a volcano that has an associated volcanic dome, either in its crater or on its flanks. Examples are Vesuvius and Mont Pelee.


A passage followed by magma in a volcano.

Continental Crust

Solid, outer layers of the earth, including the rocks of the continents.

Continental Drift

The theory that horizontal movement of the earth's surface causes slow, relative movements of the continents toward or away from one another.

Country Rock

The rock intruded by and surrounding an igneous intrusion.


A steep-sided, usually circular depression formed by either explosion or collapse at a volcanic vent.


A part of the earth's crust that has attained stability and has been little deformed for a prolonged period.

Curtain of Fire

A row of coalescing lava fountains along a fissure; a typical feature of a Hawaiian-type eruption