Earth's Interior: Composition, Structure, and Plate Tectonics (Vocabulary Flashcards)

Vocabulary flashcards covering key terms from the lecture on Earth’s interior, its layers, and plate tectonics.

accretion

Process by which small particles clump together to form a larger body, such as dust and gas coalescing to make planets and stars.

differentiation

Process during which heating causes heavier materials to sink to the center and lighter materials to rise, creating density-based layers.

continental crust

Thick, less dense crust on continents (roughly 10–70 km thick); made of light-colored rocks; lowest density among crust types (~2.7 g/cm3).

oceanic crust

Thin, more dense crust under oceans (roughly 5–7 km thick); composed mainly of dark rocks like basalt; density around 3.0 g/cm3.

mantle

Layer between crust and core; denser than crust; rich in Si, O, Mg, and Fe; olivine is a key mantle mineral; density about 3.3 g/cm3.

core

Earth’s center, a large ball of metal (mostly iron and nickel); very high density (~8 g/cm3).

lithosphere

Rigid outer shell consisting of the crust plus the uppermost mantle; floats on the underlying asthenosphere; thickness typically 10–200 km.

asthenosphere

Mushy, mostly solid mantle layer beneath the lithosphere; contains a small amount of melt; enables plate movement.

mesosphere

Lower mantle region; extremely hot but solid due to immense overlying pressure; remains solid.

Moho

Mohorovičić discontinuity; boundary between crust and mantle with a change in rock type.

core–mantle boundary

Transition zone between the mantle and the outer core where mantle rocks meet metallic core materials.

silicates

Rock-forming materials made chiefly of silicon and oxygen; dominate the Earth’s rocky crust and mantle.

olivine

Green magnesium-iron silicate mineral; major mantle constituent and contributor to mantle color; associated with the August birthstone peridot.

isostasy

Principle that the lithosphere floats in the asthenosphere; lighter/thicker lithosphere floats higher, denser/thinner lithosphere sinks lower.

continental lithosphere

Lithosphere that includes continental crust plus associated mantle; generally less dense and thicker than oceanic lithosphere.

oceanic lithosphere

Lithosphere that includes oceanic crust plus underlying mantle; denser and thinner than continental lithosphere.

plate tectonics

Theory that Earth’s lithosphere is divided into plates that move and interact at boundaries, causing earthquakes, volcanoes, and mountains.

divergent boundary

Plate boundary where plates move apart; new lithosphere is created at mid-ocean ridges as magma rises and solidifies.

convergent boundary

Plate boundary where plates collide; one plate may subduct beneath the other, destroying lithosphere.

transform boundary

Plate boundary where plates slide past one another horizontally; little creation or destruction of lithosphere.

mid-ocean ridge

Undersea mountain range formed by divergent boundaries; site of ongoing new crust formation and volcanism.

bathymetry

Measurement of ocean depths and mapping of the seafloor.

giant impact hypothesis

Moon formation theory: a Mars-sized body collided with early Earth, ejecting debris that coalesced into the Moon.

subduction

Process at convergent boundaries where a plate sinks into the mantle, recycling lithosphere.

basalt

Dark-colored igneous rock typical of oceanic crust; dense and rich in magnesium and iron.

silicate rocks

Rocks primarily composed of silicate minerals (rich in silicon and oxygen).

crust thickness

Continental crust ~10–70 km thick; oceanic crust ~5–7 km thick.

age of oceanic crust

Youngest rocks form at mid-ocean ridges; rocks get older with distance from the ridge, appearing symmetric on both sides.