Geology Review: Weathering, Sedimentary, Metamorphic Rocks, Earthquakes, and Ocean Floor

Vocabulary practice flashcards generated from lecture material on weathering, sedimentary and metamorphic rocks, earthquakes, seismology, and ocean floor evolution.

Weathering

The mechanical fragmentation (disintegration) and chemical alteration (decomposition) of rock at or near the earth's surface, involving little or no movement of weathered material.

Frost Wedging

A mechanical weathering process resulting from alternate freezing and thawing of water in cracks within rocks, expanding volume by $9\%$ to break the rock.

Exfoliation

An unloading process in which large concentric plates or shells split from the main rock mass like layers of an onion.

Spheroidal Weathering

The gradual rounding of the corners and edges of angular blocks of rocks by chemical action.

Chemical Weathering Summary Table

A table outlining the agents of weathering, products of weathering, and associated mineral groups.

Regolith

A layer of soft, unconsolidated rock material formed in place by the disintegration and decomposition of the bedrock that lies beneath it.

Pedalfer

A soil type formed in areas with abundant moisture, characterized by eluviation and leaching, with a reddish-brown color.

Pedocal

A thin soil type formed in arid or semi-arid areas with little rainfall, characterized by a lime-enriched layer called caliche and salinization.

Laterite

A very thick red soil formed in hot, wet tropical regions, characterized by intense chemical weathering and almost complete leaching of the A horizon.

Lithification

Refers collectively to all processes, including compaction and cementation, by which unconsolidated sediments are converted to solid sedimentary rocks.

Fissility

A finely layered structure along which shale splits easily, resulting from the parallel alignment of platy clay minerals.

Bioturbation

The disruption of sediment by mud-dwelling organisms, which destroys fissility and forms mudstone.

Cross-Bedding

A sedimentary structure in which small beds are inclined at an angle relative to the main sedimentary layering, indicating transport by wind or water.

Chert

A general name for a hard, dense non-detrital sedimentary rock made of microcrystalline silica, occurring as interlayered beds or irregular nodules.

Evaporites

Chemical sedimentary rocks formed when the evaporation of water concentrates dissolved ions to a point where they precipitate from solution.

Metamorphism

The solid-state transformation of pre-existing rocks into texturally or mineralogically distinct new rocks as a result of high temperature, high pressure, or chemically active fluids.

Metasomatism

Metamorphism induced by the introduction of reactive, ion-rich fluids into solid rock from an external source.

Foliation

The parallel alignment of minerals and structural features in a rock in response to directed pressure.

Index Minerals

Key minerals that indicate specific zones of metamorphic intensity across predictable sequences of temperature and pressure.

Migmatite

A metamorphic rock that shows evidence of partial melting, consisting of a mixture of igneous and metamorphic rock components.

Metamorphic Facies

A set of associated metamorphic mineral assemblages formed under specific temperature and pressure conditions during metamorphism.

Metamorphic Agents and Settings Table

A summary table outlining agents of metamorphism, types of metamorphism, plate tectonic settings, and resulting rock types.

Elastic Rebound Theory

The mechanism by which rocks bend and store elastic energy under tectonic forces until friction is overcome and slippage releases energy as an earthquake.

Focus

The point of origin within the Earth where seismic energy is first released during an earthquake.

Epicenter

The point on the Earth's surface directly above the earthquake focus.

P-Waves

Compressional or push-pull seismic body waves that travel fastest and can pass through solids, liquids, and gases.

S-Waves

Shear body waves that move material back and forth at right angles to propagation and travel exclusively through solids.

Seismic Wave Characteristics Table

A comparative table detailing manner of propagation, medium, velocity, amplitude, and period for P-waves, S-waves, and L-waves.

Benioff Zone

A narrow planar zone dipping at approximately 45^\bar{o} near deep ocean trenches where earthquake foci plunge to depths up to $700\,km$.

Mohorovicic Discontinuity

The boundary separating the low-velocity Earth crust from the higher-velocity mantle.

Continental vs. Oceanic Crust Table

A properties table comparing P-wave velocity, density, thickness, composition, and elemental enrichment between continental and oceanic crust.

Passive Continental Margin

A continental margin situated on the trailing edge of a continent away from active plate boundaries, consisting of a shelf, slope, and rise.

Guyot

An old underwater volcanic island whose top has been eroded flat by wave action before sinking below sea level.

Ophiolite Complex

A sequence of oceanic crustal layers thrust above sea level, consisting of deep-sea sediment, pillow lavas, sheeted dikes, and gabbro.