• tectonic plates – pieces of the crust or lithosphere that float on the asthenosphere– These plates form, move, and subduct

• plate tectonics– the theory that the Earth’s lithosphere is divided into tectonic plates that are in slow, constant motion, driven by convection currents in the asthenosphere

• What are boundary lines?

• Which sports have boundary lines?

• The edges of the tectonic plates meet at boundaries.

• There are 3 types of boundaries depending on how the plates are moving.– convergent – plates crash together– divergent – plates spread apart– transform – plates slide past each other

• The tectonic plates move very slowly – about as fast as your fingernail grows

• Review:

• What causes the plates to move?

• Convection currents

• Where do plates meet?

• Boundaries

• divergent boundaries – two tectonic plates spread or move apart

– Mid-ocean ridges, underwater volcanoes, and weak earthquakes are created at divergent boundaries

– Sometimes mid-ocean ridges rise above sea level. This creates a rift valley.

– rift valley – a deep valley created where pieces of Earth’s crust diverge on land (above sea level)• There is a rift valley in Iceland that people can actually

walk through• There are rift valleys in Africa as well

• convergent boundaries – two tectonic plates collide, crash into each other, or come together

– Continental crust can collide with other continental crust creating big mountains (Himalayas)

– Oceanic crust can collide with continental crust creating subduction zones, trenches, mountains (Andes – off the coast of South America), and volcanoes (the magma gets trapped under the mountain)

– strong earthquakes can also occur at convergent boundaries

• transform boundaries – two tectonic plates slide past each other

– Weak and / or moderate strength earthquakes are common at transform boundaries

– Crust is not formed or destroyed at transform boundaries

The San Andreas Fault is The San Andreas Fault is located at a transform boundarylocated at a transform boundary

Most of California Most of California is on the North is on the North

American Plate. American Plate. However, a part However, a part of the west coast of the west coast of California is on of California is on the Pacific Plate.the Pacific Plate.