Chapter 4: Rocks - Vocabulary

Comprehensive vocabulary flashcards covering the definitions of rocks, the rock cycle, igneous, metamorphic, and sedimentary classifications, and their formation processes.

Rock

A mixture of minerals, rock fragments, volcanic glass, organic matter, or other natural materials.

Rock-Forming Minerals

Common minerals found in most rocks, such as quartz, feldspar, mica, or calcite.

Rock Cycle

A model illustrating how rocks slowly change through time, demonstrating the continuous processes that create, alter, and destroy rocks without destroying matter.

Grains

Solid fragments—such as individual mineral crystals, broken mineral bits, or rock fragments—that make up a rock.

Texture

The grain size and the way grains fit together in a rock; provides clues to determine the environment in which the rock formed.

Composition

The chemical makeup or specific minerals present in a rock, providing clues about the temperature and pressure conditions under which it formed.

Magma

Molten rock located beneath Earth's surface at depths ranging from near the surface to about $150\text{ km}$, with temperatures between $650^\circ\text{C}$ and $1{,}200^\circ\text{C}$.

Lava

Molten rock that reaches Earth's surface and erupts from volcanoes.

Intrusive Igneous Rock

Igneous rock formed beneath Earth's surface when magma cools slowly, allowing atoms to arrange into large, coarse-grained mineral crystals.

Extrusive Igneous Rock

Igneous rock formed on Earth's surface when lava cools quickly upon exposure to air and water, preventing crystals from growing large.

Volcanic Glass

Extrusive rock that cools so quickly that few or no mineral crystals form, resulting in a non-crystalline, glassy structure (e.g., obsidian, pumice, scoria).

Basaltic (Mafic) Rock

Dark-colored, dense igneous rock that is rich in iron ($\text{Fe}$) and magnesium ($\text{Mg}$) but poor in silica ($\text{Si}$), forming oceanic crust.

Granitic (Felsic) Rock

Light-colored, less dense igneous rock rich in silicon ($\text{Si}$) and aluminum ($\text{Al}$), characteristic of continental crust and often coarse-grained.

Andesitic (Intermediate) Rock

Igneous rock with a mineral composition intermediate between basaltic and granitic rocks, common in volcanoes around the Pacific Rim (e.g., diorite, andesite).

Metamorphic Rock

Rock formed beneath Earth's surface when pre-existing rock changes in form, composition, or both due to intense heat, pressure, or hot watery fluids without melting.

Contact Metamorphism

The metamorphic alteration of an existing rock body caused by direct contact with hot magma.

Foliated Texture

The texture of metamorphic rocks that results when mineral grains are flattened and aligned into parallel layers or thin bands (e.g., gneiss, schist, slate).

Nonfoliated Texture

The texture of metamorphic rocks in which mineral grains do not form parallel layers or bands, instead appearing massive or interlocking (e.g., marble, quartzite).

Sediments

Loose materials such as rock fragments, mineral grains, and shell pieces that are produced by weathering and moved by wind, water, ice, or gravity.

Principle of Superposition

The geological principle stating that in undisturbed sedimentary rock layers, older layers are deposited on the bottom and younger layers lie above them.

Weathering

Mechanical or chemical surface processes that decompose or break rock into smaller fragments in place without transporting them.

Erosion

The movement and transportation of weathered rock particles by natural agents such as water, wind, ice, or gravity.

Deposition

The laying down or settling of broken rock fragments when transporting agents (wind or water) lose kinetic energy.

Lithification

The process by which loose sediment is transformed into solid rock through compaction and cementation, destroying porosity.

Compaction

The sedimentary process in which pressure from overlying layers squeezes sediment grains together and expels water from pore spaces.

Cementation

The sedimentary process where dissolved minerals (such as calcite, quartz, or hematite) precipitate out of water into pore spaces, gluing sediment grains together.

Detrital (Clastic) Sedimentary Rock

Sedimentary rock made from broken fragments of pre-existing rocks, categorized by particle size into clay, silt, sand, or gravel.

Chemical Sedimentary Rock

Sedimentary rock formed when dissolved minerals precipitate directly out of a solution, often as water evaporates from seas or lakes (e.g., rock salt, gypsum, travertine).

Organic Sedimentary Rock

Sedimentary rock formed from the accumulated remains of once-living plants or animals (e.g., coal, chalk, fossil-rich limestone, coquina).

Breccia

A coarse-grained detrital sedimentary rock composed of large, angular gravel-sized rock fragments cemented together.

Conglomerate

A coarse-grained detrital sedimentary rock composed of large, rounded gravel-sized rock fragments cemented together.