Earth's Layers and Seismic Waves - Vocabulary Flashcards

Vocabulary flashcards covering Earth’s layers, crust types, and seismic concepts.

Crust

The outermost layer of the Earth; the layer where life exists; includes continental crust (granitic) and oceanic crust (basaltic).

Mantle

Layer beneath the crust; divided into upper and lower mantle; contains the lithosphere and asthenosphere; largely solid with varying rigidity.

Outer Core

The Earth’s liquid layer composed mainly of nickel and iron; generates the planet’s magnetic field.

Inner Core

The Earth’s solid sphere at the center, composed mainly of iron-nickel.

Lithosphere

Rigid outer shell of the Earth, comprising the crust and the uppermost solid mantle (0–100 km).

Asthenosphere

Partially molten region of the upper mantle beneath the lithosphere that allows plate movement.

Mohorovičić Discontinuity (Moho)

Boundary between the crust and the mantle where seismic velocities change.

Gutenberg Discontinuity

Boundary between the lower mantle and the outer core.

Lehmann Discontinuity

Boundary between the outer core and the inner core.

Seismic Waves

Waves produced by earthquakes used to study Earth’s interior; include body waves and surface waves.

Body Waves

Seismic waves that travel through the Earth’s interior (P and S waves).

Surface Waves

Seismic waves that travel along the Earth’s surface; can cause significant ground movement.

P-Wave (Primary Wave)

Compressional body wave; can move through solids and liquids; fastest seismic wave; arrives first; particle motion is parallel to the direction of travel.

S-Wave (Secondary Wave)

Shear body wave; moves perpendicular to the direction of travel; can move only through solids; slower than P-waves and arrives after them.

Seismometer

Instrument that detects ground motion (measures seismic vibrations).

Seismograph

Instrument that records ground motion, often as part of a network of stations.

Seismogram

The recorded graphic trace of seismic waves produced by a seismometer.

Continental Crust

Crust primarily granitic in composition; less dense; thicker (about 25–70 km); ages around 3.8–4 billion years.

Oceanic Crust

Crust primarily basaltic in composition; more dense; thinner (about 7–10 km); much younger (less than ~200 million years).

Basalt

Dense, mafic rock that forms much of the oceanic crust; rich in magnesium silicates.

Granite

Less dense, felsic rock that forms much of the continental crust; rich in aluminum silicates.

Density

A measure of how compact the mass of a substance is; indicates how heavy a material is for its volume.

Volume

The measure of the three-dimensional space occupied by matter.

Surface Area

The measure of the two-dimensional area that covers the surface of a shape or object.

Discontinuity

A boundary in Earth where seismic waves change velocity as they pass through different materials.