Glossary beginning with F

Volcano Term Definitions

Faultsearch for term

A crack or fracture in the earth's surface. Movement along the fault can cause earthquakes or--in the process of mountain-building--can release underlying magma and permit it to rise to the surface.

Fault Scarpsearch for term

A steep slope or cliff formed directly by movement along a fault and representing the exposed surface of the fault before modification by erosion and weathering.

Felsicsearch for term

An igneous rock having abundant light-colored minerals.

Fire fountainsearch for term

A rhythmic vertical fountainlike eruption of lava.

Fissuressearch for term

Elongated fractures or cracks on the slopes of a volcano. Fissure eruptions typically produce liquid flows, but pyroclastics may also be ejected.

Flank Eruptionsearch for term

An eruption from the side of a volcano (in contrast to a summit eruption.)

Fluvialsearch for term

Produced by the action of of flowing water.

Formationsearch for term

A body of rock identified by lithic characteristics and stratigraphic position and is mappable at the earth's surface or traceable in the subsurface.

Fracturesearch for term

The manner of breaking due to intense folding or faulting.

Fumarolesearch for term

A vent or opening through which issue steam, hydrogen sulfide, or other gases. The craters of many dormant volcanoes contain active fumaroles.