EEPS 101 Unit 2 - Igneous Rocks & Volcanic Activity Study Guide

Vocabulary practice flashcards for EEPS 101 Unit 2 covering magma properties, igneous textures, specific rock types, volcanic features, hazards, volcano types, and tectonic settings.

Magma

Molten rock located below Earth's surface, which can contain molten rock, mineral crystals, and dissolved gases/volatiles.

Lava

Magma that reaches Earth's surface.

Volatiles

Dissolved gases contained within magma, with water vapor being especially important.

Mafic / Basaltic Magma

Magma with low silica content, rich in Fe and Mg, dark color, low viscosity, fast/fluid flow, and lower explosive potential.

Intermediate / Andesitic Magma

Magma with intermediate silica, intermediate viscosity, moderate flow rate, gray/intermediate color, and moderate explosive potential.

Felsic / Rhyolitic Magma

Magma with high silica content, high viscosity, light color, slow flow rate, high gas entrapment, and higher explosive potential.

Phaneritic Texture

A coarse-grained igneous texture with large crystals caused by slow cooling, typical of intrusive rocks.

Aphanitic Texture

A fine-grained igneous texture with small crystals too small to easily see, caused by fast cooling, typical of extrusive rocks.

Glassy Texture

An igneous texture with little or no crystal growth resulting from extremely rapid cooling.

Porphyritic Texture

An igneous rock texture featuring large crystals surrounded by a fine-grained matrix, indicating more than one cooling stage.

Vesicular Texture

An igneous rock texture containing gas-bubble holes, indicating gas was present as the material cooled.

Intrusive Igneous Rock

Igneous rock formed underground from slow-cooling magma, typically resulting in a coarse/phaneritic texture.

Extrusive Igneous Rock

Igneous rock formed at or near Earth's surface from rapidly cooling lava, typically resulting in a fine/aphanitic texture.

Bowen's Reaction Series

A model explaining the order of mineral crystallization as magma cools, where high-temperature minerals crystallize first and lower-temperature minerals crystallize later.

Basalt

A dark, mafic, fine-grained extrusive igneous rock with low silica content.

Gabbro

A dark, mafic, coarse-grained intrusive igneous rock formed by slow cooling.

Andesite

A fine-grained extrusive igneous rock of intermediate composition and gray color.

Diorite

A coarse-grained intrusive igneous rock of intermediate composition, often having a mixed light/dark appearance.

Rhyolite

A light-colored, felsic, fine-grained extrusive igneous rock with high silica content.

Granite

A light-colored, felsic, coarse-grained intrusive igneous rock in which quartz and feldspar are prominent.

Obsidian

A volcanic glass produced by very rapid cooling; often dark in color.

Pumice

A very vesicular, extremely porous, and light extrusive rock formed from gas-rich magma.

Pāhoehoe

Basaltic lava surface texture that is smooth and ropy.

ʻAʻā

Basaltic lava surface texture that is rough, broken, and jagged.

Pillow Basalt

Pillow-shaped basalt structures formed when basaltic lava erupts underwater and cools rapidly.

Columnar Jointing

Fractures formed during cooling that create column-like patterns in thick lava flows.

Lava Tubes

Tunnels formed within or beneath lava flows where lava continues flowing beneath a solidified surface layer.

Pyroclastic Material

Fragmented volcanic material ejected during an eruption.

Ash

Very fine pyroclastic particles that can harm lungs, visibility, machinery, and aircraft.

Lapilli

Small, pea-sized volcanic fragments ejected during an eruption.

Volcanic Bombs

Large volcanic fragments ejected during an eruption that may be partially molten when launched.

Tephra

A general term for unconsolidated pyroclastic material.

Pyroclastic Flow

A rapidly moving, extremely hot mixture of hot gas, ash, and volcanic fragments.

Nuée Ardente

A French phrase meaning 'burning cloud,' used as a term for a very hot pyroclastic flow.

Lahar

A dense mud or debris flow composed of volcanic debris combined with water.

Magma Chamber

An underground reservoir where magma accumulates.

Conduit

A passage through which magma moves upward inside a volcano.

Vent

An opening where volcanic material reaches Earth's surface.

Crater

A depression or opening associated with a volcanic vent.

Caldera

A large volcanic depression formed by collapse following magma withdrawal and loss of support/pressure.

Shield Volcano

A broad volcano with gentle slopes commonly formed by fluid, low-viscosity basaltic lava.

Cinder Cone

A relatively small, steep-sided volcano built from accumulated ejected pyroclastic fragments.

Stratovolcano / Composite Volcano

A large, steep-sided volcano composed of alternating layers of lava and ash/pyroclastic material, often associated with intermediate magma.

Lava Dome

A volcanic mound formed near a vent when high-silica, high-viscosity lava piles up due to poor flowability.

Fissure Eruption

An eruption occurring along an elongated crack, commonly basaltic and associated with extension.

Decompression Melting

Melting that occurs when rising mantle asthenosphere experiences a drop in pressure, generating basaltic magma at divergent boundaries.

Graben

A down-dropped crustal block formed during crustal extension and continental rifting.

Island Arc

A chain of volcanic islands associated with subduction of oceanic lithosphere beneath another oceanic plate.

Continental Volcanic Arc

A arc of volcanoes formed on continental crust resulting from subduction of oceanic lithosphere.

Hotspot

A region of persistent volcanic activity driven by a hot mantle source that is not necessarily located at a plate boundary.

Flood Basalts

Enormous volumes of very low-viscosity basaltic lava erupted across extensive geographic areas.