A term applied to igneous rocks in which the feldspar is dominantly Ca rich.

A caldera is a large, more or less circular-shaped depression (diameter >1 km) which forms when magma is either withdrawn or erupted from a shallow underground magma reservoir, resulting in the collapse of the roof rocks of the reservoir. The collapse can take place during and/or just after the caldera forming eruption. A slow subsidence of the caldera floor can continue for a long time after the end of the eruption, and arrival of new magma into the feeding system may trigger resurgence of the caldera floor and/or eruption along existing ring faults.

Caldera Collapse
The formation of a large basin-shaped volcanic depression during and/or after ab explosive eruption.

Central Vent
It is an opening at the surface of a volcanic cylindrical conduit.

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

The concluding train of seismic waves that follows the principal waves from an earthquake.

Compressional waves: see P-waves.

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

Compound Volcano
A volcano that consists of two or more vents or a volcano that has an associated dome either on the flanks or in the crater. Examples are Vesuvius and Mont Pelee.

The ‘cylindrical’ passage that magma follows in a volcano.

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.

The molten inner part of the Earth.. The outer core extends from 2500 to 3500 miles below the earth’s surface and is liquid metal. The inner core is the central 500 miles and is solid metal.

Continental shelf
The gently sloping part of the sea floor between the continental shoreline and the deep ocean basins.

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

The crust is the outermost major layer of the earth, ranging from about 10 to 65 km in thickness worldwide. The uppermost 15-35 km of crust is brittle enough to produce earthquakes.