Planet Earth Exam 1 Vocabulary Flashcards

Comprehensive vocabulary flashcards generated from Planet Earth Exam 1 concise notes, covering planetary layers, plate tectonics, mineralogy, volcanology, igneous petrology, sedimentary processes, and metamorphic geology.

Crust

Thin, solid outermost rock layer of Earth; continental crust is generally thicker and less dense than oceanic crust.

Mantle

Thick layer of mostly solid rock beneath the crust that flows very slowly and makes up most of Earth's volume.

Outer core

Layer of liquid iron and nickel beneath the mantle whose movement generates Earth's magnetic field.

Inner core

Solid sphere of iron and nickel at Earth's center, maintained in a solid state by enormous pressure despite high heat.

Lithosphere

Rigid outer layer of Earth consisting of the crust and uppermost mantle, divided into tectonic plates.

Asthenosphere

Weaker, ductile, mostly solid region of the upper mantle located directly below the lithosphere.

Mantle convection

Thermal process where hotter, less-dense material rises and cooler, denser material sinks, helping move tectonic plates.

Divergent boundary

Tectonic boundary where plates move apart and magma rises to form new crust, such as at mid-ocean ridges.

Convergent boundary

Tectonic boundary where plates move together, forming trenches, volcanoes, or mountains through subduction or continental collision.

Transform boundary

Tectonic boundary where plates slide sideways past each other, generating earthquakes without creating or destroying crust.

Mineral

Naturally occurring, solid, crystalline substance with a specific chemical composition that is generally inorganic.

Valence electrons

Outer-shell electrons of an atom that control how it forms chemical bonds.

Covalent bond

Chemical bond formed when atoms share electrons, creating strong networks such as the carbon structure in diamond.

Ionic bond

Chemical bond formed by the transfer of electrons, resulting in electrostatic attraction between positive and negative ions, as in halite.

Metallic bond

Chemical bond held together by a mobile 'sea of electrons' that allows electrical conduction.

Crystalline

Structural state of a solid characterized by a repeating, highly ordered atomic lattice.

Amorphous

Structural state of a solid lacking long-range atomic order, such as glass.

Polymorphs

Minerals that share the exact same chemical composition but possess different crystal structures, such as diamond and graphite.

Streak

The color of a mineral in its powdered form, which is often more consistent and reliable than its surface color.

Luster

The appearance of light reflecting from the surface of a mineral.

Mohs scale

A relative scale from $1$ to $10$ measuring mineral scratch resistance, spanning from talc ($1$) to diamond ($10$).

Crystal habit

The characteristic external shape in which a mineral crystal grows, such as cubic or needle-like.

Cleavage

The tendency of a mineral to break along flat structural planes governed by weak atomic bonding.

Fracture

The breakage of a mineral surface independent of cleavage planes, producing irregular or curved/conchoidal surfaces.

Silicates

The most abundant mineral group in Earth's crust and mantle, built from silicon and oxygen atoms.

Silicate tetrahedron

A fundamental anionic complex ($\text{SiO}_4^{4-}$) consisting of one central silicon atom bonded to four surrounding oxygen atoms.

Shield volcano

A broad volcano with gentle slopes constructed from fluid basaltic lava flows and typically effusive eruptions.

Stratovolcano

A tall, steep-sided volcanic cone constructed from alternating layers of lava and pyroclastic debris, often producing explosive eruptions.

Caldera

A large volcanic depression created when the roof of an underlying magma chamber collapses following a major eruption.

Pyroclastic flow

A fast-moving, ground-hugging density current composed of extremely hot gas, volcanic ash, and rock fragments.

Lahar

A flowing mixture of water, volcanic ash, and rock debris originating on a volcano.

Phaneritic texture

Coarse-grained igneous rock texture containing large, visible crystals formed by slow cooling underground.

Aphanitic texture

Fine-grained igneous rock texture containing small crystals formed by rapid cooling at or near Earth's surface.

Porphyritic texture

Igneous rock texture featuring large crystals (phenocrysts) embedded in a finer-grained groundmass, indicating dynamic multi-stage cooling.

Glassy texture

Igneous texture formed by extremely rapid cooling that prevents atomic ordering and crystal nucleation, as seen in obsidian.

Viscosity

A measure of a fluid's resistance to flow.

Lithification

The geological process of converting loose sediment into solid sedimentary rock through compaction and cementation.

Physical weathering

The mechanical disintegration of rock into smaller fragments without altering its chemical composition.

Chemical weathering

The breakdown or alteration of rock minerals through chemical processes such as dissolution, oxidation, or hydrolysis.

Protolith

The precursor or parent rock prior to undergoing metamorphic alteration.

Foliated texture

Metamorphic texture featuring planar mineral alignment or compositional banding produced by directed stress.

Slate

Low-grade, fine-grained foliated metamorphic rock derived from shale, characterized by flat, tile-like cleavage.

Phyllite

Foliated metamorphic rock containing fine mica grains that impart a characteristic silky sheen.

Schist

Medium- to high-grade foliated metamorphic rock containing visible, aligned platy minerals such as mica.

Gneiss

High-grade foliated metamorphic rock displaying prominent alternating bands of light and dark minerals.

Migmatite

A composite rock displaying mixed metamorphic and igneous textures formed when high-grade metamorphic rock undergoes partial melting.

Recrystallization

Metamorphic process in which existing mineral grains change in size or shape without altering their chemical composition.

Phase change

Metamorphic transformation in which a mineral alters its internal crystal structure without changing its chemical composition.

Index mineral

A mineral stable across specific temperature and pressure limits, used to determine the metamorphic grade of a rock.

Regional metamorphism

Widespread metamorphism driven by intense heat and directed stress over large geographic zones during mountain-building events.

Contact metamorphism

Localized metamorphism caused primarily by thermal heating from an adjacent magma body.

Shock metamorphism

Metamorphic alteration resulting from sudden, extreme pressure events, such as a meteorite impact.