Plate Tectonics Vocabulary — Lecture 4

15 vocabulary flashcards covering key terms in plate tectonics from the lecture notes.

Plate tectonics

Theory that Earth's lithosphere is divided into moving plates that ride atop the asthenosphere, interacting at boundaries to shape continents, mountains, earthquakes, and volcanoes.

Lithosphere

Rigid outer shell of Earth made up of the crust and uppermost mantle that moves as separate plates.

Asthenosphere

Plastic, partly molten layer of the mantle beneath the lithosphere that allows plate movement.

Continental crust

Thick, less dense crust composed mainly of granitic rocks (Al- and Si-rich).

Oceanic crust

Thin, dense crust mainly composed of basalt (Fe-rich) formed by mantle melting.

Basalt

Iron- and magnesium-rich, dark igneous rock common in oceanic crust.

Granite

Light-colored, silica-rich igneous rock common in continental crust.

Isostasy

Balance between crust and mantle where differences in density and thickness determine surface elevation.

Decompression melting

Melting of mantle rock due to pressure drop as material ascends, creating magma that forms oceanic crust.

Convection

Motion in fluids or partially molten rocks caused by density differences; drives mantle flow and plate motion.

Divergent boundary

Plate boundary where plates move apart; creates new crust at spreading ridges and rift valleys.

Convergent boundary

Plate boundary where plates collide; can form mountains or cause subduction and volcanism.

Transform boundary

Plate boundary where plates slide horizontally past one another, producing earthquakes along faults.

Subduction

Process where a denser plate sinks beneath another at a convergent boundary, forming trenches and volcanoes.

Mid-ocean ridge

Underwater mountain range where seafloor spreading creates new oceanic crust and basaltic volcanism.