tectonic plates – pieces of the crust or lithosphere that float on the asthenosphere

1. 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

2. 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

3. 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

4. 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

5. 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

6. 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

7. The San Andreas Fault is located at a transform boundary Most of California is on the North American Plate. However, a part of the west coast of California is on the Pacific Plate.