Sediments, Sedimentary Rocks, and Metamorphism

Comprehensive practice vocabulary flashcards covering sedimentary and metamorphic rock processes, classifications, textures, and examples as discussed in KE3007 Lecture 3.

Sedimentary Rocks

Rocks that preserve ancient environments, past climates, and fossils; they account for 70% of rocks at Earth’s surface.

Physical Weathering

The breakdown of rocks into smaller pieces through mechanical processes like freeze-thaw, salt crystals, and roots without changing composition.

Chemical Weathering

Processes such as dissolution, hydrolysis, and oxidation that change rock composition to create dissolved ions and clay minerals.

Erosion

The removal of weathered material by agents such as water, ice, wind, or gravity.

Transport

The movement of sediment from one location to another by kinetic and potential energy.

Deposition

The settling out of sediment when transport energy decreases, occurring in environments like river mouths, glaciers, or dunes.

Lithification

The five-step process by which loose sediment is converted into solid rock over thousand-to-million year timescales via compaction and cementation.

Compaction

The process where pressure from overlying material reduces water-filled pore spaces between sediment particles.

Cementation

The process where mineral-bearing groundwater circulates and precipitates dissolved material that "glues" sediment grains together.

Clastic (Detrital) Sedimentary Rocks

Sedimentary rocks made from fragments of pre-existing rocks, classified primarily by grain size.

Chemical Sedimentary Rocks

Rocks formed by precipitation from a solution, occurring through evaporation or supersaturation.

Biological (Bioclastic/Organic) Sedimentary Rocks

Rocks formed from the remains of living organisms, such as shells or plant material.

Conglomerate

A clastic sedimentary rock containing rounded particles larger than $2\,mm$.

Breccia

A clastic sedimentary rock containing angular particles larger than $2\,mm$.

Sandstone

A clastic sedimentary rock with grain sizes between $0.0625\,mm$ and $2\,mm$, typically found in rivers, beaches, and deserts.

Siltstone

A low-energy clastic sedimentary rock with grain sizes between $0.004\,mm$ and $0.0625\,mm$.

Mudstone/Shale

Very low energy clastic sedimentary rocks composed of clay-sized particles smaller than $0.004\,mm$.

Limestone

A sedimentary rock composed of $CaCO_3$ that can be formed either chemically or biologically from shells and coral.

Chalk

A soft, white limestone composed of microscopic shell fragments called coccoliths.

Coal

A biological sedimentary rock formed from compressed plant material in Carboniferous swamp forests.

Anthroposphere

The sphere of human impact on geological processes, evidenced by plastic pollution in sand or dams reducing sediment reaching the coast.

Cross-bedding

A sedimentary structure characterized by angled layers that indicate the direction of ancient currents or wind.

Metamorphism

The transformation of solid rock into new rock through heat, pressure, or fluids without the rock melting.

Contact Metamorphism

Heat-dominated, low-pressure metamorphism that occurs around igneous intrusions like magma chambers.

Regional Metamorphism

Large-scale metamorphism driven by both heat and pressure, primarily occurring in continent-continent collision zones.

Foliation

The parallel alignment of minerals such as mica or chlorite perpendicular to the direction of maximum pressure.

Metamorphic Aureole

A narrow zone surrounding an igneous intrusion where the adjacent rocks have been baked and recrystallized.

Whin Sill

A dolerite intrusion in the UK that created contact metamorphism in surrounding Carboniferous rocks at approximately $1100\text{-}1200^\circ\text{C}$.

Slate

A low-grade foliated metamorphic rock formed from mudstone that splits into perfect planes.

Schist

A medium-grade metamorphic rock derived from mudstone where shiny mica minerals are visible.

Gneiss

A high-grade metamorphic rock characterized by a banded appearance of light and dark mineral layers.

Quartzite

A hard, massive, non-foliated metamorphic rock produced from quartz-rich sandstone.

Marble

A non-foliated metamorphic rock with a sugary texture formed from the recrystallization of calcite in limestone.