Volcanism, Mountain Building, Metamorphic Rocks, and The Rock Cycle – Vocabulary Flashcards

Vocabulary flashcards covering key terms from volcanism, mountain building, metamorphic rocks, and the rock cycle as presented in the notes.

Volcanism

The processes associated with the eruption of molten rock (magma) onto a planet’s surface; a constructive igneous process that builds volcanoes, lava, gases, rocks, and new crust.

Magma

Melted rock stored beneath the surface; the source of lava during eruptions.

Lava

Molten rock that erupts onto the surface as a liquid.

Pyroclastic debris

Fragmented volcanic material ejected during eruptions, including ash, pumice, and volcanic bombs.

Tephra

All airborne pyroclastic material ejected during an eruption, including ash, bombs, and blocks.

Crater

A circular or oval depression at the summit or vent of a volcano.

Central vent

The main conduit through which magma ascends to the surface.

Lava flows

Streams of molten rock that flow down the volcano’s surface after eruption.

Magma chamber

Underground reservoir of magma feeding a volcano.

Viscosity

The resistance of a liquid to flow; controls lava behavior and eruption style.

Basaltic lava (mafic)

Low-silica, low-viscosity lava typical of mid-ocean ridges and hotspots.

Andesitic lava (intermediate)

Lava with intermediate silica content and viscosity.

Rhyolitic lava (felsic)

High-silica, high-viscosity lava that traps gases and is often highly explosive.

Pahoehoe

Smooth, ropey, flowing basaltic lava with a glossy surface.

AA (lava)

Rough, blocky lava that cools and thickens, trapping gases.

VEI (Volcanic Explosivity Index)

A relative scale (0–8) measuring the explosiveness of volcanic eruptions.

Shield volcano

Broad, gently sloping volcano built by low-viscosity lava streams.

Stratovolcano (composite volcano)

Steep-sided volcano formed by alternating layers of lava flows and pyroclastic debris, often above subduction zones.

Cinder cone

Small, steep-sided volcano built from tephra and volcanic fragments from a single vent.

Caldera

Large, basin-like depression formed when a magma chamber empties and the summit collapses.

Spreading centers

Mid-ocean ridges where tectonic plates pull apart, causing volcanism.

Subduction zones

Regions where one plate sinks beneath another, forming arc volcanism and stratovolcanoes.

Hotspots

Mantle plumes causing intraplate volcanism away from plate boundaries (e.g., Hawaii, Yellowstone).

Plinian eruption

A highly explosive eruption that ejects tall columns of ash and gas.

Pyroclastic flows

Dense, fast-moving flows of volcanic fragments and hot gases that race down slopes.

Lahars

Volcanic mudflows formed when ash mixes with water and flows downslope.

Ash clouds

Clouds of volcanic ash released into the atmosphere that can disrupt air travel.

Volcanic gases

Gases emitted by volcanoes (e.g., H2O, CO2, SO2) that influence hazards and climate.

Alc VEI scale

See VEI; a relative measure of eruption explosiveness from 0 to 8.

Plinian eruptions

Very explosive eruptions with tall eruption columns and widespread tephra.

Mount St. Helens (1980)

Notable Plinian-style eruption (VEI 5) with lateral blast and debris avalanche.

Laki eruption (1783–1784)

VEI 4 fissure eruption in Iceland with toxic gas release and climate impacts.

Krakatoa (1883)

VEI 6 eruption with global climatic effects and dramatic sunsets.

Eyjafjallajökull (2010)

Eruption producing a major ash cloud that disrupted European air travel.

Santorini caldera

Massive caldera-forming eruption in the Aegean; linked to ancient myths.

Mount Tambora (1815)

VEI 7 eruption; caused global temperature drop and the Year Without Summer.

Mount Vesuvius

Historic VEI-5 eruption that destroyed Pompeii; iconic volcanic event.

Stratovolcano (composite) hazards

Explosive, ash-rich eruptions and pyroclastic flows commonly associated with subduction-zone volcanism.

Types of volcanoes at plate boundaries

Volcano types formed at spreading centers, subduction zones, and hotspots.

Volcano monitoring

Techniques used to track gas emissions, deformation, seismic activity, and thermal changes to forecast eruptions.

Islands of volcanic activity in the Solar System

Non-Earth volcanism examples (Io, Titan, Mars) demonstrating planetary volcanism.

Caldera-forming eruptions

Major eruptions that collapse the volcano and create large calderas.

Mantle plume (hotspot) volcanism

Volcanism resulting from a hot mantle plume beneath a tectonic plate.

Pleistocene and Holocene volcanic activity

Periods of significant volcanic eruptions shaping modern landscapes.

Volcanic hazard assessment

Evaluation of risks from pyroclastic flows, lahars, ash clouds, gases, earthquakes, and climate effects.

Volcanology

The science of studying volcanoes, their eruptions, products, and hazards.

Rocks formed by volcanism

Igneous rocks formed from cooled magma, either at the surface (extrusive) or underground (intrusive).

Folding

Ductile deformation caused by compressional forces that creates curved rock layers.

Faulting

Fracturing and displacement of rocks due to stress; forms faults.

Crustal deformation

Structural changes in the crust from tectonic processes, often spanning large distances.

Stress

Applied force acting on rocks (compression, tension, shear) that can cause deformation.

Strain

The physical change in shape or size of a rock resulting from stress.

Elastic deformation

Temporary, reversible deformation before rocks fracture.

Ductile deformation

Permanent bending of rocks without fracturing.

Brittle deformation

Fracturing and breaking of rocks under stress.

Shear

Deformation from sliding past one another along a plane.

Compression

Pushing rocks together, causing shortening and thickening.

Tension

Pulling rocks apart, causing extension.

Differential stress

Stress with different magnitudes in different directions (three principal stresses: shear, compression, tension).

Elastic limit

Maximum stress a material can withstand elastically before permanent deformation.

Hooke’s Law

Relationship where stress is proportional to strain in the elastic region.

Joints

Fractures with little or no displacement; little movement along the fracture.

Faults

Planar fractures with displacement along which rocks have moved.

Hanging wall

The block above a fault plane.

Footwall

The block below a fault plane.

Dip-slip faults

Faults that slip along the dip direction; include normal and reverse (thrust) types.

Normal fault

Hanging wall moves down relative to the footwall.

Reverse fault

Hanging wall moves up relative to the footwall.

Thrust fault

Low-angle reverse fault with large displacement.

Strike-slip faults

Faults that slide horizontally; right-lateral (dextral) or left-lateral (sinistral).

Dextral (right-lateral)

Block across the fault appears to move to the right.

Sinistral (left-lateral)

Block across the fault appears to move to the left.

Transform fault

Plate boundary where two blocks slide past one another in a horizontal motion.

Oblique-slip fault

Faults with both dip-slip and strike-slip movement.

Anticline

A fold arching upward with the oldest rocks at its center.

Syncline

A fold bending downward (trough) with youngest rocks at its center.

Horst

Raised block between two normal faults.

Graben

Sinked block between two normal faults.

Orogeny

Mountain-building episode caused by crustal convergence and crustal thickening.

Divergent margins

Plate boundaries where plates move apart, often with rifting and faulting.

Convergent margins

Plate boundaries where plates collide, leading to mountain building via collision and thrusting.

Intrusions (igneous)

Magma bodies that crystallize below the surface, forming plutons and other intrusive rocks.

Mountain building through volcanism

Mountains can also form from volcanic activity and extrusive igneous rocks.

Uplift and erosion

Process that exposes buried rocks, contributing to mountain landscapes.

Rock Cycle

A continuous set of processes by which rocks are transformed among igneous, sedimentary, and metamorphic forms.

Extrusive igneous rock

Igneous rock formed when magma erupts and cools at the surface.

Intrusive igneous rock

Igneous rock formed when magma crystallizes below the surface.

Weathering and erosion

Mechanical and chemical breakdown of rocks and removal of fragments by natural agents.

Magma crystallization

Cooling of magma to form igneous rocks, either at the surface or underground.