Unit 4 Vocab

Igneous Rocks

Rocks formed from the cooling and crystallization of magma or lava, classified as either intrusive or extrusive.

Lava

Magma that flows out onto Earth’s surface.

Partial Melting

The process in which different minerals melt into magma at different temperatures, altering its composition.

Bowen’s Reaction Series

A sequential, predictable pattern in which minerals crystallize from cooling magma, forming a dual-branched series.

Fractional Crystallization

A process where different minerals crystallize from magma at different temperatures, removing elements from the magma.

Intrusive Rocks

Coarse-grained igneous rocks formed when molten rock cools slowly inside Earth’s crust.

Extrusive Rocks

Fine-grained igneous rocks that form when molten rock cools quickly on Earth's surface.

Basaltic Rocks

Dark-colored igneous rocks with lower silica contents, rich in iron and magnesium, primarily consisting of plagioclase and pyroxene.

Granitic Rocks

Light-colored, intrusive igneous rocks with high silica content.

Texture (in geology)

The size, shape, and distribution of the crystals or grains that make up a rock.

Porphyritic Texture

Rock texture characterized by large, well-formed crystals surrounded by finer-grained crystals.

Vesicular Texture

Characterized by containing vesicles, or holes, formed by gas bubbles in the rock.

Pegmatites

Igneous rocks with extremely large-grained minerals that may contain rare ores such as lithium and beryllium.

Kimberlites

Rare, ultramafic rocks that can contain diamonds and other minerals formed under high pressures.

Sediments

Small pieces of rock that are moved and deposited by water, wind, glaciers, and gravity.

Lithification

The processes that transform sediments into sedimentary rock, including compaction and cementation.

Cementation

A process of sedimentary rock formation where dissolved minerals precipitate out of groundwater, binding the sediment grains together.

Bedding

Horizontal layering in sedimentary rock, ranging from a few millimeters to several meters thick.

Graded Bedding

A type of bedding where particle sizes become progressively heavier and coarser towards the bottom layers.

Cross Bedding

Depositional feature of sedimentary rock formed as inclined layers of sediment are carried forward across a horizontal surface.

Clastic Sedimentary Rocks

Most common type of sedimentary rocks formed from accumulated loose sediments classified by particle size.

Clastic

Rocks composed of rock and mineral fragments produced by weathering and erosion.

Porosity

The percentage of open spaces between grains in a mineral.

Evaporites

Chemical sedimentary rocks formed when dissolved minerals in water reach saturation due to evaporation.

Foliated

Describes metamorphic rocks like schist or gneiss, whose minerals are squeezed under high pressure and arranged in wavy layers.

Nonfoliated

Describes metamorphic rocks such as quartzite and marble, composed mainly of blocky crystal shapes.

Regional Metamorphism

Process affecting large areas of Earth's crust, producing belts of varying grades depending on pressure and temperature.

Contact Metamorphism

Local effect that occurs when molten rock meets solid rock.

Hydrothermal Metamorphism

Occurs when hot water reacts with rock, altering its mineralogy and chemistry.

Rock Cycle

The continuous set of processes by which rocks are transformed from one type to another.