Volcanoes
Vents or fissures in the earth's crust through which gases, molten rock, or lava , and solid fragments are discharged.
A caldera on Mount Etna.
An old lava flow on Mount Etna.
Active Volcano
A volcano that is erupting. Also, a volcano that is not presently erupting, but that has erupted within historical time and is considered likely to do so in the future.
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
The simplest type of volcano, built from particles and blobs of congealed lava ejected from a single vent.
Composite Volcano
A steep volcanic cone built by both lava flows and airborne rocks and ash. Also known as a stratovolcano.
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.
Dormant Volcano
Literally, "sleeping." The term is used to describe a volcano which is presently inactive but which may erupt again. Most of the major Cascade volcanoes are believed to be dormant rather than extinct.
Extinct Volcano
A volcano that is not presently erupting and is not likely to do so for a very long time in the future.
Hot-spot Volcanoes
Volcanoes related to a persistent heat source in the mantle.
Maar
A volcanic crater that is produced by an explosion in an area of low relief, is generally more or less circular, and often contains a lake, pond, or marsh.
Magma Chamber
An area filled with magma that lies beneath a volcano.
Monogenetic
A volcano built by a single eruption.
Phreatic Eruption (Explosion)
An explosive volcanic eruption caused when water and heated volcanic rocks interact to produce a violent expulsion of steam and pulverized rocks. Magma is not involved.
Phreatomagmatic
An explosive volcanic eruption that results from the interaction of surface or subsurface water and magma.
Plinian Eruption
An explosive eruption in which a steady, turbulent stream of fragmented magma and magmatic gases is released at a high velocity from a vent. Large volumes of tephra and tall eruption columns are characteristic.
Repose
The interval of time between volcanic eruptions.
Shield Volcano
A gently sloping volcano in the shape of a flattened dome and built almost exclusively of gentle lava flows.
Stratovolcano
A steep volcanic cone built by both lava flows and airborne rocks and ash. Also known as a composite volcano.
Strombolian Eruption
A type of volcanic eruption characterized by jetting of clots or fountains of fluid basaltic lava from a central crater.
Volcanic Ash
Lava from a volcano that is in the form of chunks smaller than an apple, about the size of marbles.
Volcanic Bomb
A large lump of lava thrown out of a volcano during an eruption. A bomb usually starts as a flying blob of lava, but solidifies as it falls to the ground.
Volcanic Dust
Lava in the form of small, tiny particles thrown from a volcano during an eruption.
See also: Aa, Andesite, Basalt, Caldera, Lava, Magma, Pumice, Pyroclastic, Richter Scale, Seismic, Seismograph, Tephra.
Subjects: Geology