Earthquakes and Plate Tectonics - Vocabulary Flashcards

A vocabulary set covering earthquakes, plate tectonics, weathering/erosion, and related features.

Focus (hypocenter)

The location within the Earth’s crust where an earthquake originates.

Epicenter

The point on the Earth's surface directly above the focus.

Seismic Waves

Energy waves produced by earthquakes that travel through the Earth’s layers.

P Waves (Primary Waves)

Fastest seismic waves; travel through both fluids and solids; push–pull motion; arrive first.

S Waves (Secondary Waves)

Slower seismic waves; travel only through solids; move rock particles up and down or side to side, perpendicular to the direction of travel.

Surface Waves

Seismic waves that travel near the surface; lower frequency; arrive after body waves and cause most earthquake damage.

Magnitude

Energy released at the earthquake’s source; measured from seismograph readings.

Intensity

Strength of shaking at a location, estimated from eyewitness accounts and damage.

Seismograph

Instrument used to measure and record seismic waves and magnitude.

Plate Tectonics

Theory that Earth’s lithosphere is divided into moving plates whose interactions cause geologic activity.

Mantle

Layer beneath the crust where convection currents drive plate movement.

Convection Currents

Cyclic movement of mantle rock caused by temperature differences, powering plate motion.

Lithosphere

Rigid outer layer of Earth, including the crust and upper mantle.

Plate Boundary

Edge where two tectonic plates meet; boundaries can be divergent, convergent, or transform.

Divergent Boundary

Plates move apart, creating new crust at mid-ocean ridges or rift valleys.

Convergent Boundary

Plates move toward each other; may involve subduction and/or mountain building.

Transform Boundary

Plates slide past one another horizontally, often causing earthquakes.

Subduction

One plate moves beneath another at a convergent boundary, producing earthquakes and volcanoes.

Trenches

Deep oceanic troughs formed at subduction zones.

Island Arc

Chain of volcanic islands formed by subduction of oceanic crust beneath another plate.

Hot Spot

Localized plume of hot mantle that rises toward the surface, causing volcanic activity away from plate boundaries.

Oceanic Crust

Thin, dense crust made mostly of basalt; sinks beneath continental or other oceanic crust at subduction zones.

Continental Crust

Thicker, less dense crust that forms continents and mountains when collision occurs.

Fault

A fracture in rocks where movement has occurred.

Strike‑Slip Fault

Horizontal movement of rocks along a fault, typically at transform boundaries.

Normal Fault

Dip-slip fault where the block above moves downward relative to the block below; common at divergent boundaries.

Reverse Fault

Dip-slip fault where the block above moves upward relative to the block below; common at subduction/convergent boundaries.

Rock Cycle

Processes by which rocks change between igneous, sedimentary, and metamorphic forms.

Igneous

Rock formed when magma cools and crystallizes.

Sedimentary

Rock formed from weathering, erosion, compaction, and cementation of sediments.

Metamorphic

Rock formed from existing rocks transformed by heat and pressure.

Weathering

Chemical and physical breakdown of rocks into sediment.

Chemical Weathering

Chemical changes in minerals, such as oxidation, hydrolysis, and carbonation.

Oxidation

Chemical reaction of minerals with oxygen (e.g., rust formation).

Hydrolysis

Water reacting with minerals to weaken rock structures.

Carbonation

Carbon dioxide in rain forms carbonic acid, contributing to weathering.

Physical (Mechanical) Weathering

Breaking rocks without changing their chemical composition (e.g., frost wedging, abrasion, plant growth).

Erosion

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

Deposition

Sediments deposited to form landforms such as deltas, flood plains, dunes, estuaries, and beaches.

Volcano

A vent in the crust through which magma erupts; part of volcanism.

Volcanism

The process of volcanic eruption and related activity, often linked to plate tectonics and hot spots.

Density

Mass per unit volume (commonly expressed in g/cm^3).