Chapter Seven: Plate Tectonics Lesson 3: The Theory of ...

Chapter Seven: Plate Tectonics Lesson 3: The Theory of Plate Tectonics

Plate tectonics: Earth's surface is made up of rigid slabs of rock, or plates, which move with respect to each other

Constant motion

Tectonic: Geologists use this word to describe the forces that shape Earth's surface and the rock structures that form as a result

Lithosphere: the cold and rigid outermost rock layer Made up of the crust and the solid, uppermost mantle Tectonic plates are the pieces of the lithosphere (ride on top of it)

Divergent plate boundary: where two plates separate (pull away from each other)

Seafloor spreading ? at a mid-ocean ridge, lava erupts, cools and forms new crust

Transform plate boundary: where two plates slide past each other (horizontally)

San Andreas Fault in California

Convergent plate boundary: where two plates collide (come together) Subduction: the denser plate sinks below the more buoyant plate o Oceanic crust & continental crust Oceanic crust will subduct under the continental crust forming a volcano (picture) o Continental crust & continental crust Both will collide and form mountains (picture)

Convection: the circulation of material caused by differences in temperature and density

Hot air rises while cold air sinks (same concept on the inside of the Earth)

Basal drag: a force that causes motion from the convection currents in the mantle

Ridge push: a force that moves the plates away from the ridge at mid-ocean ridges

Moves the lithosphere in opposite directions away from the mid-ocean ridges

Slab pull: a force that pulls the plates down into the Earth in the subduction zone

Scientists are still uncertain about which force has the greatest influence on plate motion.

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