Rocks: Materials of the Solid Earth - Flashcards

Flashcards covering rock cycle concepts, igneous rock formation and textures, weathering, sedimentary rocks and lithification, and metamorphic rocks and textures from the lecture notes.

What is the Rock Cycle?

The rock cycle describes the interactions among Earth's systems in the origin and interconversion of igneous, sedimentary, and metamorphic rocks; any rock can become any other given the right sequence of events.

What initiates the Basic Rock Cycle?

The cycle begins with magma formed by melting in the crust and upper mantle; magma rises, erupts as lava, or crystallizes within the crust; cooling is crystallization or solidification.

What is weathering?

The transformation of rock to reach equilibrium with its environment; occurs as mechanical and chemical weathering and is followed by erosion that transports weathered material.

What is lithification?

The process of converting loose sediment into solid rock by compaction and cementation.

What is metamorphism?

Transformation of preexisting rock due to changes in temperature, pressure, and chemical environment, resulting in new mineralogy and texture; progresses from low-grade to high-grade.

What are the two main metamorphic settings?

Contact metamorphism (temperature rise from intrusion) and regional metamorphism (pressure and high temperature during mountain building).

What are the agents of metamorphism?

Heat, confining pressure, and chemically active fluids (hydrothermal fluids).

What drives metamorphism?

Differential stress and chemically active fluids promote deformation, recrystallization, and mineral changes.

What is extrusive igneous rock?

Igneous rock formed by the rapid cooling of lava at the surface, producing fine-grained textures.

What is intrusive igneous rock?

Igneous rock formed by the cooling of magma below the surface, producing coarse-grained textures.

What is magma?

Melted rock within the mantle or crust; rises because it is less dense than surrounding rock.

What is lava?

Magma that reaches the Earth's surface.

What is Bowen's reaction series?

A sequence showing which minerals crystallize at specific temperatures during cooling, starting with olivine, then pyroxene and plagioclase, then amphibole and biotite, then muscovite and potassium feldspar, with quartz last.

What is magmatic differentiation?

Formation of one or more secondary magmas from a single parent magma, often due to crystal removal and changing melt composition; crystals may settle at the bottom.

What does felsic mean in igneous rocks?

Rocks rich in light silicates such as quartz and potassium feldspar; commonly lighter in color and high in silica; often with some dark silicates.

What does mafic mean in igneous rocks?

Rocks rich in dark silicates like olivine and pyroxene; higher in iron and magnesium; generally darker and denser (basalt, gabbro).

What does intermediate (andesitic) composition mean?

Between felsic and mafic; mixture of light and dark silicates; at least 25% dark silicate minerals; common at continental margins.

What does ultramafic mean in igneous rocks?

Rocks dominated by dark minerals such as olivine and pyroxene; rare at Earth’s surface and primarily constitute the mantle.

What is granite in igneous rocks?

A coarse-grained felsic rock formed from slow cooling of magma at depth; major component of continental crust.

What is rhyolite?

A fine-grained extrusive igneous rock that is the volcanic, rapid-cooling equivalent of granite; light-colored and often vesicular.

What is obsidian?

Natural volcanic glass; usually felsic composition but glassy texture formed by rapid cooling.

What is pumice?

A vesicular volcanic glass that forms when gas-rich lava froths; very light and usually floats in water.

What is andesite?

A medium-gray extrusive rock with fine-grained or porphyritic texture; typically contains plagioclase and amphibole; common at Pacific margin volcanoes.

What is diorite?

A coarse-grained intrusive rock that is the intrusive equivalent of andesite; little or no visible quartz.

What is basalt?

The most common extrusive igneous rock; dark and fine-grained; rich in pyroxene, olivine, and plagioclase; common at oceanic crust and volcanic islands.

What is gabbro?

Coarse-grained intrusive equivalent of basalt; not commonly exposed at the surface; major component of oceanic crust.

What is the texture variety fine-grained vs coarse-grained in igneous rocks?

Fine-grained: rapid cooling at or near the surface; crystals too small to see; coarse-grained: slow cooling at depth; visible crystals.

What is porphyritic texture?

A rock texture with large crystals (phenocrysts) set in a matrix of smaller crystals.

What is vesicular texture?

Texture with numerous voids left by gas bubbles that remained during solidification.

What is glassy texture?

Texture formed when rocks cool rapidly, producing a glass with no organized crystal structure.

What is pyroclastic texture?

Texture composed of rock fragments ejected during explosive volcanic eruptions, including ash, bombs, and blocks.

What are the three groups of sedimentary rocks?

Clastic (detrital), Chemical, and Organic (biochemical) sedimentary rocks.

What is lithification in sedimentary rocks?

The combination of compaction and cementation that turns loose sediment into rock.

What are the main features of sedimentary rocks?

Form in layers (strata or beds); have bedding planes; contain fossils that clue past environments and ages.

What are clastic sedimentary rocks by particle size?

Conglomerate (rounded gravel), Breccia (angular gravel), Sandstone (sand grains), Shale (clay), Siltstone (silt with some clay).

What are chemical sedimentary rocks?

Rocks formed by precipitation of minerals from solution, often via evaporation; examples include limestone, chert, rock salt, gypsum.

What are organic sedimentary rocks?

Rocks formed from carbon-rich remains of organisms; coal is a key example.

What is lithification in detail?

Involves compaction from weight of overlying sediment and cementation from mineral-rich water filling pores, cementing grains together.

What are fossils used for in sedimentary rocks?

Clues to ancient environments and ancient life; help correlate rocks of the same age across distances.

What is metamorphism in brief?

Transformation of preexisting rock into a new rock due to increased temperature, pressure, and chemically active fluids, creating new minerals and textures.

What are the two main metamorphic textures?

Foliated textures from differential stress (parallel mineral alignment) and nonfoliated textures from minimal deformation and stable minerals.

What are common foliated metamorphic rocks?

Slate, phyllite, schist, and gneiss.

What are common nonfoliated metamorphic rocks?

Marble and quartzite.

What drives metamorphism in rocks?

Heat from magma or burial, confining pressure, differential stress, and hydrothermal fluids that catalyze recrystallization.