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

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

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

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









Documents

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