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