Plate Tectonics

Plate TectonicsEQ: How do lithospheric plates move and how do they affect the Earths surface?1An Idea Before its TimeIn 1912, Alfred Wegener proposed the idea of Continental DriftHe suggested that all of the continents were once joined together to form a supercontinent

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3PangaeaWegener called this super landmass Pangaea and believed that it broke apart 200 million years agoPangaea means all landAt first, his theory was not acceptedUnable to explain how the continents drifted apart

4Evidence down the RoadYears later came important observations that supported Continental DriftFossil Clues- similar fossils found in South America and Africa and others found in Africa, Australia, India, South America, and Antarctica.

5Evidence down the Road

Rock evidence- similar rock structures are found on different continents, such as this mountain belt that end at one coastline, only to reappear on a landmass across the ocean.6Evidence down the RoadClimate Clues- glacier deposits and rock surfaces shows that parts of South America, Africa, India, and Australia were once covered with glaciers

7Quick Check:What is Continental Drift?

What 3 pieces of evidence support the idea of Pangaea?The idea that all of the continents were once joined togetherFossils, Rock Clues (Mountains), and Climate Clues (Glaciers)

8A New Theory EmergesWegener could not provide an explanation of exactly what made the continents move. New technology lead to findings which then lead to a new theory called plate tectonics

9This New EvidenceWith new technologies, scientists discovered a mountain chain on the ocean floor known as the Mid-Ocean RidgeMid-ocean ridges are underwater chains that run through Earths ocean basin

The Mid-Atlantic Ridge, the longest mountain chain in the world10Seafloor SpreadingMid-ocean ridges are places where the sea-floor spreadsAs tectonic plates move away from each other, the seafloor spreads apart and magma rises to fill in the gapsThe hot magma contacts ocean water, cools and hardens becoming new rockThis process is known as Seafloor Spreading11

12Plate TectonicsThe Theory of Plate Tectonics was developed in 1960s and combines the theories of Continental Drift and Sea-Floor Spreading. Scientist believe the Earths crust and part of the upper mantle is broken into 13 sections that make up the plates which move on top of the asthenosphere13

14Convection CurrentsConvection currents, originating deep within the mantle, provides the energy that drives plate tectonicThese currents rotate in circular patterns, carrying heat upward

http://www.absorblearning.com/media/attachment.action?quick=12p&att=2775 15Plate BoundariesDivergent boundaries are the place where two plates move apart.Convergent boundaries form where two plates move together.Transform fault boundaries are where two plates slide past each other without the production or destruction of the lithosphere.

16Convergent Boundary

17Divergent Boundary

18Plate Tectonic Discussion Questions:Explain why Wegeners theory of Continental Drift was not accepted at first.Explain what is Plate Tectonics and what causes the movement of plate tectonics.What are the 3 plate boundaries and describe them.

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