Earth Materials, Plate Tectonics, and Igneous Processes

Comprehensive vocabulary flashcards generated from lecture materials covering Earth Materials, Plate Tectonics, and Igneous Processes.

Mineral

A naturally occurring, inorganic solid with a specific chemical composition, an ordered atomic structure (crystal lattice), and specific physical properties.

Rock

An aggregate of minerals or disordered solids in clastic or crystalline form that has undergone lithification or crystallization, defined by the size, composition, and arrangement of its clasts or crystals.

Kimberlite Pipe

A deep volcanic pipe originating in the mantle where mantle peridotite infused with high $CO_2$ and $H_2O$ produces explosive boiling, jettisoning mantle-formed diamonds to the surface.

Mohs Hardness Scale

A relative scale ranging from 1 (talc) to 10 (diamond) used to measure mineral hardness relative to reference items such as a fingernail ($2.5$), copper penny ($3.5$), glass plate ($5.5$), steel nail ($6.5$), and masonry drill bit ($8.5$).

Cleavage

The tendency of a mineral to split or crack along the weakest planar surfaces of its crystal lattice.

Element Abundance in Earth's Crust

The relative abundance of elements in the upper crust by weight percentage, dominated by Oxygen ($46.6\%$) and Silicon ($27.7\%$), followed by Aluminum ($8.1\%$), Iron ($5\%$), Calcium ($3.6\%$), Sodium ($2.8\%$), Potassium ($2.6\%$), and Magnesium ($2.1\%$).

Silicate Mineral Group

The most abundant mineral family in Earth's crust, consisting of a silicon atom bonded to 2 or 4 oxygen atoms ($SiO_2$ tetrahedra).

Decompression Melting

The process where mantle rock melts due to a decrease in pressure without a change in temperature, such as at spreading ridges.

Dehydration Melting

The melting process that occurs when water trapped in subducting oceanic sediments is released, lowering the melting temperature of overlying mantle rocks.

Oceanic Crust

Thinner ($5\,km$), younger ($< 200\,Ma$), and denser mafic/basaltic lithosphere enriched in $Fe$ and $Mg$ that rides lower and gets subducted.

Continental Crust

Thicker ($15\,km$), older ($< 3.8\,Ga$), and less dense felsic/andesitic lithosphere enriched in $Si$, $Al$, and $K$ that rides higher and is never subducted.

Pangea

An ancient supercontinent whose former existence is supported by matching fossil distributions (such as Glossopteris and Mesosaurus) and identical ancient rock assemblages across modern continents.

Morley-Vine-Matthews Hypothesis

The proposal that symmetric magnetic anomaly patterns surrounding mid-ocean ridges are created by seafloor spreading combined with periodic reversals of Earth's magnetic field recorded in erupting basalt.

Hot Spot

A stationary mantle convection plume that burns through the overriding lithospheric plate, creating a linear chain of age-progressive volcanoes.

Divergent Margin

A plate boundary where tectonic plates move apart from one another, creating new lithosphere via continental rifts or mid-ocean spreading ridges.

Convergent Margin

A plate boundary where tectonic plates move toward each other, leading to ocean lithosphere subduction or continental mountain-building collision.

Transform Margin

A plate boundary where tectonic plates slide horizontally past one another without creating or destroying lithosphere.

Failed Rift

An inactive arm of a triple junction rift system that stopped spreading (such as the Reelfoot Rift), which frequently controls the location of major river channels.

Passive Margin

A quiet continental border created by rifting that accumulates thick loads of sediment without active tectonic boundary motion.

Seismic Tomography

A subsurface imaging technique using earthquake wave propagation speeds to map three-dimensional structures inside the mantle, highlighting cold subducting plates where seismic waves speed up.

Phaneritic Texture

A coarse-grained igneous rock texture formed by slow cooling of magma beneath Earth's surface, allowing visible crystals time to grow.

Aphanitic Texture

A fine-grained igneous rock texture produced by rapid cooling of magma at or near Earth's surface, leaving little to no time for crystal growth.

Porphyritic Texture

An igneous rock texture featuring two distinct crystal sizes: large phenocrysts embedded in a finer groundmass, indicating a two-stage cooling history.

Phenocryst

An outsized crystal in a porphyritic igneous rock that grew significantly larger than the surrounding finer matrix.

Groundmass

The fine-grained matrix surrounding phenocrysts in a porphyritic igneous rock.

Mafic Igneous Rock

Igneous rock enriched in Magnesium and Iron ($Fe$, $Mg$), dark in color, with higher melting temperatures ($700^\circ\text{C}$ to $1200^\circ\text{C}$) and lower silica content (e.g., basalt, gabbro).

Felsic Igneous Rock

Igneous rock enriched in Feldspar and Silica ($Si$, $Na$, $K$), light in color, with lower melting temperatures ($\approx 600^\circ\text{C}$ to $700^\circ\text{C}$) and higher silica content (e.g., rhyolite, granite).

Obsidian

A disordered volcanic glass ($SiO_2$) formed by instant cooling of felsic lava, lacking a crystal structure and breaking with conchoidal fractures.

Bowen's Reaction Series

The systematic sequence in which silicate minerals crystallize from a cooling magma, ranging from high-temperature mafic minerals (olivine, pyroxene) to low-temperature felsic minerals (muscovite, quartz).

Viscosity

A fluid's resistance to flow; mafic magmas have low viscosity and flow easily as lavas, whereas felsic magmas have high viscosity and form explosive ash clouds.

Pahoehoe

A smooth, ropy-textured lava flow produced by low-viscosity mafic basaltic magma.

Aa

A rough, jagged, and blocky lava flow formed from cooler, higher-viscosity basaltic lava.

Vesicle

A cavity or bubble in a volcanic rock created by gas exsolving and expanding while the rock was still molten.

Shield Volcano

A broad, gently sloping volcanic landform built by successive flows of low-viscosity basaltic lava over non-explosive eruptions (e.g., Kilauea).

Stratovolcano

A steep-sided, composite volcanic cone formed from alternating layers of viscous lava flows and explosive pyroclastic tephra (e.g., Mt. Shasta, Popocatépetl).

Volcanic Dome

A mound-shaped landform produced by the slow extrusion and accumulation of highly viscous felsic lava directly above or inside a volcanic vent.

Nuée Ardente

A glowing avalanche composed of a dense, superheated cloud of gas, ash, and rock debris traveling down a volcano at speeds up to $500\,km/h$.

Lahar

A destructive volcanic mudflow or debris flow consisting of pyroclastic material, rock fragments, and water.

Volcanoes of the World Distribution

The global clustering of volcanic landforms along active plate boundaries (such as the Pacific Ring of Fire) and mantle hot spots.

Volcanic Ash Activity Centers (VAAC)

An international warning system monitoring atmospheric volcanic ash clouds to issue alerts and prevent aircraft jet engine failure.