Chapter 4 Section 5 The Theory of Plate Tectonics

The lithosphere is broken into separate sections called plates. The geological theory that states that pieces of Earth’s lithosphere are in constant, slow motion, driven by convection currents in the mantle is plate tectonics.

The edges of Earths plates meet at plate boundaries Faults , or beaks in the Earths crust form along the boundaries There are three kinds of plate boundaries.

Spreading boundaries The place where two plates move apart Spreading boundaries are also called divergent boundaries Most occur along the mid-ocean ridges They also occur on land forming a deep valley called a rift valley.

Colliding boundaries A colliding boundary is a place where two plates come together or collide Colliding boundaries are also called convergent boundaries When two oceanic plates collide, subduction occurs. When an oceanic plate and continental plate collide the subduction of the oceanic plate occurs. When two continental plates collide mountain ranges form.

Sliding boundaries A sliding boundary is a place where two plates slip past each other in opposite directions Sliding boundaries are also called transform boundaries Crust is neither created or destroyed