GEOL 101 Exam 02 Study Guide: Igneous Rocks, Volcanism, and Sedimentary Processes

Vocabulary flashcards based on the GEOL 101 Exam 02 Study Guide covering magma, igneous rock textures and compositions, intrusive bodies, volcanic activity, and weathering mechanisms.

Igneous rocks

Rocks formed by the cooling and solidification of magma.

Magma vs. Lava

Magma is molten rock located internally beneath the Earth's surface, while lava is molten rock located externally on the surface.

Volatiles

Dissolved gases in magma melt, which include water vapor, carbon dioxide, and sulfur dioxide.

Viscosity of magma

A magma's resistance to flow; it is controlled by heat, where hotter magma results in faster flow / lower viscosity.

Aphanitic texture

An igneous texture formed by a rapid rate of cooling, characterized by small crystals and the potential presence of vesicles.

Phaneritic texture

An igneous texture formed by slow cooling, characterized by large, visible crystals.

Glassy texture

An igneous texture resulting from a rapid rate of cooling.

Porphyritic texture

An igneous texture characterized by a mix of both small and large crystals within the rock.

Intermediate composition

An igneous rock composition containing $53/66\%$ dark silicate materials.

Mafic composition

An igneous rock composition containing $46/52\%$ dark silicate materials.

Ultramafic composition

An igneous rock composition containing $38/45\%$ dark silicate materials.

Basaltic magma

A magma type characterized by mild eruptions, low silica content, and low viscosity.

Evolution of magma

Processes that change the chemical composition of magma, specifically fractional crystallization, assimilation, and magma mixing.

Dike

A vertical intrusive igneous body.

Sill

A horizontal intrusive igneous body.

Batholith

A large magma deposit forming an intrusive igneous body.

Stratovolcanoes

A hazardous type of volcano characterized by explosive eruptions.

Physical weathering

The mechanical breakdown of a mineral without altering its chemical composition (examples include frost wedging, thermal expansion, biological activities, and unloading).

Chemical weathering

The breakdown of rocks that alters their chemical composition, with water acting as the principal agent.

Dissolution

A chemical weathering process aided by small amounts of acid present in water.

Hydrolysis

A chemical weathering reaction where a hydrogen ion attacks and replaces other ions, such as feldspar weathering to form kaolinite.

Oxidation

Any chemical weathering reaction wherein electrons are lost from one element.

Carbonates vs. Silicates weathering rate

Carbonate minerals weather faster than silicate minerals.