Plate Tectonics: Key Concepts and Evidence for Earth’s Lithosphere

What is the lithosphere?

The rigid outer layer of the Earth, including the crust and uppermost mantle, broken into tectonic plates.

What drives plate tectonics?

Convection in the mantle, slab pull, and ridge push.

Divergent boundary

Boundary where plates move apart; creates new crust at mid-ocean ridges.

Convergent boundary

Boundary where plates collide; subduction zones or mountain building.

Transform boundary

Boundary where plates slide past each other; causes earthquakes (e.g., San Andreas Fault).

Evidence for plate tectonics

Fit of continents, fossil distribution, paleomagnetism, seafloor spreading, earthquake/volcano patterns.

Paleomagnetism

The record of Earth's magnetic field preserved in rocks; supports seafloor spreading.

Subduction zone

Region where one plate sinks beneath another into the mantle.

Mid-ocean ridge

Underwater mountain range formed by upwelling magma at divergent boundaries.

Hotspot

Stationary mantle plume creating volcanic chains (e.g., Hawaiian Islands).