theory of plate tectonics
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Theory of plate tectonics. Continental drift hypothesis. Before the theory of plate tectonics in the 1960’s, there was Alfred Wegener’s hypothesis of continental drift. He thought all the continents were once connected to make a single supercontinent called Pangea. Pangea 300 million years ago. - PowerPoint PPT PresentationTRANSCRIPT
Theory of plate Theory of plate tectonicstectonics
Continental drift hypothesisContinental drift hypothesis Before the theory of plate tectonics Before the theory of plate tectonics
in the 1960’s, there was Alfred in the 1960’s, there was Alfred Wegener’s hypothesis of continental Wegener’s hypothesis of continental drift.drift.
He thought all the continents were He thought all the continents were once connected to make a single once connected to make a single supercontinent called Pangea.supercontinent called Pangea.
Pangea 300 million years Pangea 300 million years agoago
Evidence that supported Evidence that supported PangeaPangea
Why do the continents move?Why do the continents move?
The theory of plate tectonics states that the The theory of plate tectonics states that the Earth’s lithosphere is broken up into plates. Earth’s lithosphere is broken up into plates. These plates continually move and change These plates continually move and change shape and size.shape and size.
When plates move, they cause earthquakes When plates move, they cause earthquakes and volcanoes along the plate boundaries.and volcanoes along the plate boundaries.
Plates move slow-on average 5 cm a year!Plates move slow-on average 5 cm a year! Plate motion is caused by convective Plate motion is caused by convective
currents in the asthenospherecurrents in the asthenosphere
Types of plate boundariesTypes of plate boundaries Divergent- plates pull apartDivergent- plates pull apart Real life example: atlantic ocean and Real life example: atlantic ocean and
east african rift valleyeast african rift valley Causes: earthquakes, sea floor Causes: earthquakes, sea floor
spreading, rift valleys, and mid ocean spreading, rift valleys, and mid ocean ridgesridges
divergentdivergent Mid ocean ridgeMid ocean ridge East African rift East African rift
valleyvalley
Convergent continental Convergent continental continentalcontinental
2 continents collide-push together2 continents collide-push together Example: how Appalachian Example: how Appalachian
mountains formed and the mountains formed and the Himalayan mountainsHimalayan mountains
Causes earthquakes and mountainsCauses earthquakes and mountains
Appalachian Appalachian mountains formmountains form
Himalayan Himalayan mountainsmountains
Convergent oceanic oceanicConvergent oceanic oceanic 2 ocean plates collide-push together2 ocean plates collide-push together Example: islands of japan, indonesiaExample: islands of japan, indonesia Causes: earthquakes, subduction Causes: earthquakes, subduction
zones, tsunamis, volcanic islandszones, tsunamis, volcanic islands
Convergent oceanic Convergent oceanic continentalcontinental
An ocean plate and continental plate An ocean plate and continental plate collidecollide
Examples: Cascade volcanic Examples: Cascade volcanic mountains in northwestern US (Mt st mountains in northwestern US (Mt st Helens)Helens)
Causes: earthquakes, volcanic Causes: earthquakes, volcanic eruptions, tsunamiseruptions, tsunamis
Transform faultTransform fault 2 plates slide past each other2 plates slide past each other Example: San andreas fault in Example: San andreas fault in
CaliforniaCalifornia Causes only earthquakesCauses only earthquakes
What evidence supports the What evidence supports the theory of plate tectonics?theory of plate tectonics?
Paleomagnetism- alternating layers Paleomagnetism- alternating layers of rock at the bottom of ocean floors of rock at the bottom of ocean floors show normal and reverse polarityshow normal and reverse polarity
Earthquake patternsEarthquake patterns
Hot spotsHot spots