GEOS 212 Lecture 3 Flashcards: Hotspots, Subduction Zones & Volcanoes

Vocabulary practice flashcards generated from GEOS 212 Lecture 3 covering hotspots, subduction zones, plate motion calculations, and volcanic settings.

Hot spot

A long-lived, relatively stationary source of magma, often located above a mantle plume, that creates a chain of volcanoes as a tectonic plate moves overhead.

Mantle plume

A column of unusually hot mantle material that rises toward the surface from deep within Earth, often originating near the core-mantle boundary at approximately $2900\,\text{km}$ deep.

Subduction zone

A convergent boundary where one lithospheric plate (typically dense oceanic crust) sinks beneath another plate into Earth's mantle.

Ocean trench

A long, narrow, extremely deep depression in the ocean floor formed at a subduction zone where the subducting oceanic plate bends downward.

Shield volcano

A broad, gently sloping volcano built by repeated eruptions of fluid, low-viscosity basaltic lava that travels long distances.

Stratovolcano

A steep, conical composite volcano built from alternating layers of lava flows, ash, and volcanic debris, characterized by sticky andesitic magma and explosive eruptions.

Caldera

A large, basin-shaped depression formed when a volcanic eruption rapidly empties a magma chamber, causing the overlying ground roof to collapse.

Volcanic arc

A chain of volcanoes formed on the overriding plate above a subduction zone, fed by magma generated in the underlying mantle wedge.

Volcanic island arc

A curved chain of volcanic islands created by ocean-ocean subduction, such as Japan, the Aleutian Islands, or Tonga.

Andesite

An intermediate-composition volcanic rock with moderate silica content ($\sim 57\text{--}63\%\,\text{SiO}_2$) that is more viscous than basalt and frequently fuels explosive eruptions.

Ring of Fire

A global belt of intense seismic and volcanic activity surrounding the Pacific Ocean, spanning approximately $40,000\,\text{km}$ and containing about $75\%$ of Earth's active volcanoes.

Challenger Deep

The deepest known point in Earth's ocean, reaching approximately $10,971\,\text{m}$ below sea level in the Mariana Trench.

Spreading center

A divergent plate boundary (such as a mid-ocean ridge) where tectonic plates pull apart and rising mantle magma generates new oceanic crust.

Continental rift

A divergent boundary within a continent where the continental lithosphere is pulled apart, causing crustal thinning, faults, and volcanism.

Viscosity

A physical measure of a fluid's resistance to flow; basaltic magma has low viscosity (runny), whereas silica-rich magmas have high viscosity (sticky).

Effusive eruption

A volcanic eruption characterized by the steady, non-explosive outpouring of low-viscosity lava onto Earth's surface.

Pyroclastic flow

A high-speed, extremely hot, and lethal avalanche of gas, ash, and rock fragments produced during explosive volcanic eruptions.

Lahar

A destructive volcanic mudflow or debris flow consisting of water, volcanic ash, and rock fragments that travels rapidly down river valleys.

Supervolcano

A volcano capable of producing monumental eruptions of the highest magnitude (VEI 8), driven by massive magma reservoirs.

90° East Ridge

An underwater linear volcanic ridge in the Indian Ocean formed as a track from the Indian Plate's northward movement prior to its collision with Asia.