Earth Science - Volcanoes and Other Igneous Activity (not main)

Comprehensive vocabulary flashcards covering the characteristics of magma, eruption types, volcanic landforms, and intrusive igneous activity from Chapter 6 of Tarbuck and Lutgens' Earth Science.

Mount St. Helens (1980)

The largest historic eruption in North America, which erupted a cubic kilometer of ash and lowered the volcano's height by $1350\,feet$.

Kilauea

A Hawaiian volcano that began erupting in 1983; it is characterized by non-explosive eruptions of fluid basaltic lavas.

Basaltic (mafic) Magma

Magma rich in dark silicates that originates from the partial melting of the upper mantle; it has the least silica content ($\sim 50\%$) and the highest eruptive temperatures ($1000$-$1250^\circ\text{C}$).

Granitic (felsic) Magma

Magma rich in light silicates resulting from the melting of continental crust; it has the highest silica content ($\sim 70\%$) and the greatest viscosity.

Viscosity

The resistance of a fluid to flow; in magma, higher silica content corresponds to higher viscosity and more explosive eruptions.

Pahoehoe lava

A type of basaltic lava flow that exhibits a twisted, ropy texture.

Aa lava

A type of basaltic lava flow characterized by a rough, jagged, and blocky texture.

Pillow lavas

Basaltic lavas that solidify underwater, typically occurring along divergent plate boundaries on the ocean floor.

Volcanic Ash

Fine, glassy pyroclastic fragments that are less than $2\,mm$ ($0.08\,inch$) in size.

Lapilli (Cinders)

Pyroclastic materials that range in size from $2\,mm$ to $64\,mm$ ($0.08$-$2.5\,inches$).

Volcanic Bombs

Pyroclastic fragments larger than $64\,mm$ that are ejected as hot, incandescent lava.

Crater

A steep-walled depression at the summit of a volcano, generally less than $1\,kilometer$ in diameter.

Caldera

A large summit depression typically greater than $1\,kilometer$ in diameter, often formed by the collapse of a volcano.

Shield Volcano

The largest type of volcano, broad and slightly dome-shaped, built primarily from large volumes of fluid basaltic lava (e.g., Mauna Loa).

Cinder Cone

A small volcano with steep slopes built mainly from ejected basaltic cinder-sized fragments.

Composite Volcano (Stratovolcano)

A large, classic-shaped volcano composed of interbedded lava flows and pyroclastic debris, known for violent eruptions (e.g., Fujiyama or Mount St. Helens).

Pyroclastic flow

A highly destructive mixture of hot gas, ash, and rock that moves down volcanic slopes at speeds exceeding $200\,km/h$ and temperatures over $1100^\circ\text{C}$.

Lahar

A volcanic mudflow caused by the interaction of ash and rock with water, often following stream valleys.

Fissure Eruptions

Eruptions where fluid basaltic lava is extruded from crustal fractures (fissures), sometimes forming basalt plateaus such as the Columbia River Plateau.

Volcanic Neck

The resistant conduit of a volcano that remains standing after the surrounding cone has been removed by erosion (e.g., Ship Rock, New Mexico).

Dike

A tabular intrusive body that cuts across existing bedding surfaces.

Sill

A tabular intrusive body that is injected along bedding planes.

Batholith

The largest type of intrusive body (pluton), defined as being greater than $10\,km$ wide and often forming the core of mountain ranges.

Decompression Melting

The process of generating magma that occurs when hot mantle rock rises to shallower depths and lower pressures.

Hot Spot

A localized volcanic region in the overriding plate caused by a plume of heat rising from the mantle.