PLATE TECTONICS

Lithospheric plates Lithosphere is made up of 12 large plates and about 20 smaller ones Plates are solid and float on the asthenosphere Convection currents in the asthenosphere make the plates move

Continental and Oceanic plates Continental plates are usually less dense Oceanic plates are under the ocean and made of more dense rock

Plate Boundaries There are 3 main types of plate boundaries: Divergent ( moving apart) Convergent (moving together) Transform (moving past each other)

Divergent Boundaries On land - produce rift valleys Under the ocean - mid- ocean ridges such as in the Atlantic As the plates separate, magma rises into the space and hardens Volcanoes and shallow earthquakes occur

Convergent boundaries One plate may move under the other (subduction zone) Deep earthquakes and volcanoes occur Mountains form when one plate is pushed up

Types of convergent boundaries Oceanic - oceanic: creates chains of islands (ex. Phillipines)

Oceanic - continental: oceanic plate subduct under continental plate; creates deep ocean trenches and coastal mountain ranges

Continental - continental: mountain ranges ex. Himalaya

Transform boundaries Plates slide past each other causing fault lines and earthquakes Ex. San Andreas Fault