Lecture_8_-_Igneous_rocks

Volcanism

The process by which magma and associated gases rise through the Earth’s crust and are extruded onto the surface or into the air.

Eruptive Products

The substances that come out of a volcanic eruption, including lava (liquids), pyroclasts (solids), and gases.

Viscosity

A measure of a fluid's resistance to flow; in volcanic terms, it's affected by the silica content of the magma.

Pyroclasts

Ejected fragments of rock and lava that cool and harden while in flight during a volcanic eruption.

Decompression Melting

The process by which rock melts due to a decrease in pressure, typically occurring in divergent plate boundaries.

Mafic Magma

Magma that is rich in magnesium and iron, typically producing basalt lavas.

Felsic Magma

Magma that is rich in silica and typically produces granite or rhyolite.

Composite Volcano

Volcanoes formed from a combination of explosive activity and lava flow, characterized by steep slopes and layered deposits.

Shield Volcano

A broad, slightly domed volcano formed by the accumulation of fluid mafic basaltic lava flows.

Lahar

A destructive mudflow on the slopes of a volcano, composed of volcanic debris and water.

Tuff

A type of rock formed from volcanic ash and fragments that have been compacted together.

Bowen's Reaction Series

A series that explains the order of mineral crystallization from cooling magma, indicating how different igneous rocks form.

Aphanitic Texture

A fine-grained texture characteristic of igneous rocks that cool quickly, preventing large crystal formation.

Phaneritic Texture

A coarse-grained texture characteristic of igneous rocks that cool slowly, allowing larger crystals to form.

Glassy Texture

A texture of igneous rocks that results from very rapid cooling, preventing crystal formation.

Magma vs. Lava

Magma is molten rock beneath the Earth's surface, while lava is magma that has erupted onto the Earth's surface.

Volcanic Ash

Very fine particles of rock and glass formed during explosive volcanic eruptions.

Geothermal Gradient

The rate of increasing temperature with respect to increasing depth in the Earth's interior.

Hot Spot

An area in the Earth's mantle where magma is generated and rises, leading to volcanic activity independent of tectonic plates.

Intrusive Igneous Rocks

Rocks formed from magma that cools and solidifies beneath the Earth's surface.

Extrusive Igneous Rocks

Rocks formed from lava that cools and solidifies on the Earth's surface.