Ch 5 Volcanoes and Volcanic Hazards Flashcards
Aa flow
A type of lava flow that has a jagged, blocky surface.
Aerosols
Tiny solid and liquid particles suspended in the atmosphere.
Andesite
A gray, fine-grained igneous rock, primarily of volcanic origin and commonly exhibiting a porphyritic texture.
Atmosphere
The gaseous portion of a planet, the planet’s envelope of air. One of the traditional subdivisions of Earth’s physical environment.
Basalt
A fine-grained igneous rock of mafic composition.
Bed
Strata
Caldera
A large depression typically caused by collapse or ejection of the summit area of a volcano.
Cinder cone
A rather small volcano built primarily of ejected lava fragments that consist mostly of pea- to walnut-size lapilli.
Color
A phenomenon of light by which otherwise identical objects may be differentiated.
Column
A feature found in caves that is formed when a stalactite and stalagmite join.
Composite cone
A volcano composed of both lava flows and pyroclastic material.
Composite volcano
Composite cone
Compound
A substance formed by the chemical combination of two or more elements in definite proportions and usually having properties different from those of its constituent elements.
Conduit
A pipelike opening through which magma moves toward Earth’s surface. It terminates at a surface opening called a vent.
Confining pressure
Stress that is applied uniformly in all directions.
Continental volcanic arc
Mountains formed in part by igneous activity associated with the subduction of oceanic lithosphere beneath a continent. Examples include the Andes and the Cascades.
Convergent plate boundary
A boundary in which two plates move together, resulting in oceanic lithosphere being thrust beneath an overriding plate, eventually to be reabsorbed into the mantle. It can also involve the collision of two continental plates to create a mountain system.
Crater
The depression at the summit of a volcano or a depression that is produced by a meteorite impact.
Crust
The very thin, outermost layer of Earth.
Decompression melting
Melting that occurs as rock ascends due to a drop in confining pressure.
Density
A property of matter defined as mass per unit volume.
Divergent plate boundary
A boundary in which two plates move apart, resulting in upwelling of material from the mantle to create new seafloor.
Dome
A roughly circular upfolded structure.
Earthquake
Vibration of Earth produced by the rapid release of energy.
Eruption column
Buoyant plumes of hot, ash-laden gases that can extend thousands of meters into the atmosphere.
Fissure
A crack in rock along which there is a distinct separation.
Fissure eruption
An eruption in which lava is extruded from narrow fractures or cracks in the crust.
Flood
The overflow of a stream channel that occurs when discharge exceeds the channel’s capacity. The most common and destructive geologic hazard.
Flood basalts
Flows of basaltic lava that issue from numerous cracks or fissures and commonly cover extensive areas to thicknesses of hundreds of meters.
Flow
A type of movement common to mass-wasting processes in which water-saturated material moves downslope as a viscous fluid.
Focus (earthquake)
The zone within Earth where rock displacement produces an earthquake.
Fumarole
A vent in a volcanic area from which fumes or gases escape.
Glass (volcanic)
Natural glass that is produced when molten lava cools too rapidly to permit recrystallization. Volcanic glass is a solid composed of unordered atoms.
Glassy
A term used to describe the texture of certain igneous rocks, such as obsidian, that contain no crystals.
Head (stream)
The beginning or source area for a stream. Also called the headwaters.
Hot spot
A concentration of heat in the mantle, capable of producing magma that, in turn, extrudes onto Earth’s surface. The intraplate volcanism that produced the Hawaiian Islands is one example.
Intensity (earthquake)
A measure of the degree of earthquake shaking at a given locale, based on the amount of damage.
Intraplate volcanism
Igneous activity that occurs within a tectonic plate, away from plate boundaries.