Plate Tectonics

The Earth’s crust is divided into 12 major plates which are moved in various directions. Earth’s plates float on top of mantle similar to ice cubes in a bowl of water

Tectonic Plates

“Plates” of lithosphere are moved around by the underlying hot mantle convection cells.

Different Types of Boundaries

Sea-floor spreading: process by which new ocean floor is formed

Many rift valleys form at divergent plate boundaries Many rift valleys form at divergent plate boundaries. The depression created by the rifting plates is the rift valley.

Divergent Boundary – Arabian and African Plates Arabian Plate Red Sea African Plate

Mid-oceanic ridges – divergent boundary in the middle of the ocean; forms new sea floor. underwater mountain chains that run through the Earth’s Basins Magma rises to the surface and solidifies and new crust forms Older Crust is pushed farther away from the ridge

Divergent Boundary – Iceland

Convergent Boundary Forms mountains, e.g. European Alps, Himalayas

Eurasian Plate Indian Plate Himalayan Mountains

Subduction: At a convergent boundary where continental crust pushes against oceanic crust, the oceanic crust which is thinner and more dense than the continental crust, sinks below the continental crust.

Transform Boundary: place where two tectonic plates slide past each other horizontally