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Melt (liquid rock), crystals (solid minerals), and volatiles (dissolved gases such as H₂O, CO₂, SO₂).

Magma that reaches the surface.

In the crust and upper mantle where rocks partially melt.

Silicon, oxygen, aluminum, iron, calcium, sodium, potassium, and magnesium.

A rock that forms when magma or lava cools and solidifies.

Determined by cooling rate, depth, and presence of volatiles.

Coarse-grained; crystals visible to the eye due to slow cooling underground.

Fine-grained; crystals too small to see due to fast cooling at or near the surface.

Mixed crystal sizes; formed by slow cooling then rapid cooling.

Lava cooled so quickly that no crystals formed (e.g., obsidian).

Contains gas bubbles; formed as gas escapes during cooling (e.g., pumice, scoria).

Fragmental; formed from ash, bombs, and rock fragments welded together.

Slow cooling → large crystals; fast cooling → small crystals.

Formed from magma cooled slowly underground.

Formed from lava cooled rapidly at or near the surface.

Very low silica (<44%), high iron and magnesium; forms mantle rocks like peridotite.

Low silica (44-60%), dark colored, dense; forms basalt and gabbro.

Moderate silica (60-70%), gray or andesitic; forms andesite or diorite.

High silica (70-76%), light color, viscous; forms granite or rhyolite.

Higher silica = lighter color; lower silica = darker color.

Lower silica (mafic) = higher density; higher silica (felsic) = lower density.

More silica → higher viscosity (thicker lava).

Minerals crystallize in predictable order from high to low temperature as magma cools.

Plagioclase feldspar changes from Ca-rich to Na-rich as temperature decreases.

Olivine → Pyroxene → Amphibole → Biotite as magma cools.

Olivine and Ca-rich plagioclase.

Quartz, muscovite, and K-feldspar.

Minerals that crystallize first melt last.

Source rock composition, partial melting, and magma mixing.

Increasing temperature, decreasing pressure (decompression), or adding water.

As mantle rock rises, pressure decreases faster than temperature, causing melting.

Mid-ocean ridges and continental rifts.

Water released from the subducting slab lowers melting temperature of mantle rock.

When magma rises through continental crust, it assimilates crustal material and becomes more felsic.

Rising mantle plumes undergo decompression melting forming basaltic magma.

They derive from partial melting of ultramafic mantle peridotite.

Controlled by composition (minerals) and texture (crystal size).

Granite ↔ Rhyolite, Diorite ↔ Andesite, Gabbro ↔ Basalt, Peridotite ↔ Komatiite.

Large body of intrusive igneous rock formed beneath the surface.

Very large irregular intrusive body exceeding 100 km².

Smaller intrusive body (<100 km²).

Sheet-like intrusion parallel to existing rock layers.

Vertical or cross-cutting sheet of igneous rock.

Dome-shaped intrusion that pushes overlying layers upward.

A vent or opening through which magma and gases reach the surface.

Determined by magma composition, viscosity, gas content, and temperature.

Resistance to flow; controlled mainly by silica content and temperature.

H₂O, CO₂, SO₂, and minor Cl and F.

When gases cannot escape magma, pressure builds up, causing explosive eruptions.

Allows gases to escape easily, producing gentle lava flows.

Traps gases, creating explosive eruptions.

Broad, gently sloping; mafic lava flows; low viscosity; non-explosive (e.g., Mauna Loa).

Basalt, scoria, and minor obsidian.

Small, steep-sided cone of pyroclastic fragments; mafic; short-lived.

Steep, symmetrical; alternating lava and ash; intermediate-felsic; explosive (e.g., Mt. St. Helens).

Steep mound formed from highly viscous felsic lava.

Massive outpourings of mafic lava from fissures covering large areas.

From plume heads spreading under the lithosphere and melting extensively.

Broad, flat region formed by stacked flood-basalt flows.

Large circular depression formed by collapse after massive eruption.

Hot, fast-moving clouds of gas, ash, and debris racing down volcano slopes.

Volcanic mudflows of ash and water that travel down valleys.

Lava flows, gas release, local fires, and minor explosions.

Pyroclastic flows, ash fall, lahars, and climate effects.

A molten or semi-molten rock fragment ejected during eruption that solidifies in the air.

Rock composed of consolidated volcanic ash.

Rock made of large angular pyroclastic fragments.

Frothy volcanic glass with abundant vesicles; very light.

Vesicular basalt; darker and denser than pumice.

Geologists measure earthquakes, gas emissions, ground deformation, and temperature changes.

Causes flood basalts.

Produces long-term hotspot volcanism.

From lithification of sediment, precipitation from solution, or accumulation of biological material.

Clastic (detrital), Chemical, and Organic/Biochemical.

Weathering, erosion, transport, deposition, and lithification.

The breakdown of rock at or near Earth's surface.

The removal and transport of weathered material by wind, water, ice, or gravity.

Physical disintegration (frost wedging, root pry, abrasion).

Decomposition by water and atmospheric gases (dissolution, hydrolysis, oxidation).

Limestone dissolving in acidic water forming caves.

Feldspar reacting with water to form clay minerals.

Iron-bearing minerals reacting with oxygen to form rust-colored oxides.

Rock composition, climate, presence of water, and biological activity.

Movement of sediments by water, wind, ice, or gravity.

Energy of the transporting medium.

Further travel → smaller, rounder, better-sorted particles.

The uniformity of grain size; well-sorted = single size, poorly-sorted = mixed.

Degree to which edges of a grain have been worn smooth.

The degree of weathering and transport a sediment has undergone.

Boulder, cobble, pebble, sand, silt, clay.

Features formed during or after deposition, such as bedding, ripples, or mudcracks.

Layering within sedimentary rocks due to variations in deposition.

Inclined layers within horizontal beds; indicates current direction.

Layers with grain size decreasing upward; indicates settling from suspension.

Small wave-like features formed by water or wind movement.

Polygonal cracks formed when wet mud dries; indicates exposure to air.

Past life, climate, and depositional environment.

Conglomerate, breccia, sandstone, siltstone, shale.

Rounded gravel-sized clasts cemented together.

Angular gravel clasts; minimal transport.

Sand-sized grains; can be quartz-rich (mature).

Fine-grained; smooth feel.

Very fine-grained, fissile layers; forms in quiet water.

Limestone, dolostone, evaporites (rock salt, gypsum), chert, coal.

From accumulation or precipitation of calcium carbonate.

From magnesium replacing calcium in limestone.

From evaporation of saline water (rock salt, gypsum).

Formed from compacted plant material in swampy environments.

Forms from silica from microscopic organisms like radiolarians.

Can tell us about the past environment, climate, biological activity, and geologic history.

Includes coal, oil, natural gas, groundwater, and building materials.

Locations where sediment accumulates with distinct physical and biological conditions.

Examples include alluvial fans, rivers (fluvial), deserts (eolian), glacial deposits, lakes, and swamps.

Examples include deltas, beaches, lagoons, estuaries, wetlands.

Examples include shallow continental shelves, reefs, deep-marine basins.

Change in shape, size, or volume of rock due to applied stress.

Stress = force per unit area; strain = deformation caused by stress.

The three main types are compression, tension, and shear.

The three types are elastic (temporary), brittle (fracture), and ductile (bend/flow).

Occurs in the shallow crust under low temperature and pressure.

Occurs in the deep crust under high temperature and pressure.

A crack in rock with no movement across it.

A fracture along which movement has occurred.

Has parts including hanging wall (above fault) and footwall (below fault).

Characterized by tensional stress; hanging wall moves down relative to footwall.

Characterized by compressional stress; hanging wall moves up relative to footwall.

Involves horizontal motion due to shear stress (right-lateral or left-lateral).

A low-angle reverse fault common in mountain belts.

The compass direction of the line formed by intersection of a rock layer with a horizontal plane.

The angle and direction of slope of a rock layer or fault from horizontal.

An upfold; the oldest rocks are in the center.

A downfold; the youngest rocks are in the center.

A single bend in otherwise horizontal layers.

Planar alignment of minerals due to pressure during metamorphism.

A solid-state change of a rock's texture and mineralogy due to heat, pressure, or fluids.

The original rock before metamorphism.

Heat, pressure, differential stress, and chemically active fluids.

Growth of new mineral grains without melting.

Local heating by intrusion of magma; forms non-foliated rocks.

Large-scale metamorphism from mountain-building; produces foliated rocks.

Alteration of rock by hot, chemically active fluids.

Metamorphism from deep burial and pressure increase.

Metamorphism caused by meteorite impacts.

The degree of metamorphic change from low to high temperature and pressure.

Shale → Slate → Phyllite → Schist → Gneiss.

Slate.

Gneiss.

Very fine-grained, foliated rock that splits easily along planes.

Glossy, wavy foliation; slightly coarser than slate.