Igneous Rocks

Earth Science

Magma

The liquid or molten rock found beneath the Earth’s surface.

Lava

Molten rock (magma) that has erupted from a volcano or crack in the Earth’s surface.

Crystallization

The process of taking material from its liquid form and gradually freezing until organized into a crystal structure.

Mineralogy

The scientific study of minerals, including their composition, structure, properties, and distribution.

Silicate Minerals

A large group of minerals primarily composed of silicon and oxygen, including quartz and feldspar.

Nonsilicate Minerals

Minerals that do not contain silicon and oxygen in their structure, like carbonates and sulfates.

Ferromagnesian Silicates

Silicate minerals with significant amounts of iron and magnesium, resulting in dark color and high density.

Nonferromagnesian Silicates

Silicate minerals with little or no iron or magnesium, featuring lighter colors and elements like sodium.

Texture

Refers to the size, shape, and arrangement of mineral grains within a rock.

Bowen’s Reaction Series

A model that describes the sequence of mineral crystallization from cooling magma.

Fractional Crystallization

The process of different minerals solidifying from cooling magma at varying temperatures.

Assimilation

The incorporation of surrounding rock materials into a body of magma, altering its composition.

Xenolith

A fragment of rock embedded within another rock type, often found in igneous rocks.

Phaneritic Texture

An igneous rock texture characterized by large, visible crystals.

Porphyritic Texture

An igneous rock texture with large crystals embedded in a finer-grained matrix.

Phenocrysts

Relatively large crystals distinguishable from smaller grains in an igneous rock.

Groundmass

The fine-grained matrix within an igneous rock that contains larger crystals.

Rhyolite

A fine-grained, light-colored, extrusive igneous rock rich in silica.

Granite

A coarse-grained, intrusive igneous rock primarily composed of quartz, feldspar, and mica.

Diorite

A coarse-grained, dark-colored, intrusive igneous rock with visible crystals.

Andesite

A fine-grained igneous rock formed from magma that crystallizes outside of a volcano.

Gabbro

A coarse-grained, dark-colored, intrusive igneous rock formed from slow cooling of magma.

Basalt

A fine-grained extrusive igneous rock characterized by a dark color and rich in iron and magnesium.

Glassy Texture

A rock texture with no visible mineral crystals, resembling colored glass.

Obsidian

A naturally occurring volcanic glass formed from rapidly cooled lava.

Igneous Rock

Forms from the cooling and crystallization of molten rock.

Sedimentary Rock

Forms from the lithification of sediment.

Metamorphic Rock

Forms when existing rocks undergo heat and/or pressure.

Cooling History

The rate of cooling affects the texture of igneous rocks, with slow cooling leading to coarser textures.

What is Bowen's Reaction Series?

A model explaining the sequence of mineral formation through heating and cooling of igneous rocks.

What controls volcanic eruption violence?

Magma composition, viscosity, and dissolved gas content influence eruption explosiveness.