Earth's Interior Layers Flashcards

Grade 7 · Science · Flashcards

Key terms for Earth's four layers, their compositions, and how scientists study Earth's interior.

Flashcards

Crust: Earth's thin, outermost solid layer; oceanic crust = basalt (dense, thin); continental crust = granite (less dense, thick).
Mantle: Thickest layer of Earth (70–2,900 km); solid silicate rock that flows very slowly over time.
Asthenosphere: The upper portion of the mantle that is hot and partially plastic; tectonic plates float on it.
Outer core: Liquid layer of iron and nickel (2,900–5,100 km depth); generates Earth's magnetic field.
Inner core: Solid sphere of iron and nickel at Earth's center; held solid by extreme pressure.
Seismic waves: Vibrations from earthquakes; P-waves pass through solids and liquids; S-waves only through solids.
Seismograph: Instrument that detects and records seismic waves from earthquakes.
Geothermal gradient: The increase in temperature as depth inside Earth increases.
Magnetic field: The invisible protective field around Earth generated by convection in the liquid outer core.
Lithosphere: Rigid outer layer including the crust and uppermost mantle; broken into tectonic plates.
P-waves: Primary seismic waves; compressional waves that travel through solids and liquids; fastest seismic waves.
S-waves: Secondary seismic waves; shear waves that only travel through solids; stop at the liquid outer core.
Oceanic crust: Thin, dense crust made of basalt forming ocean floors; 5–10 km thick.
Continental crust: Thick, less dense crust made of granite-like rock forming continents; 30–70 km thick.