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Continents change Position over Time

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Presentation on theme: "Continents change Position over Time"— Presentation transcript:

1 Continents change Position over Time

2 The development of Plate tectonics/ Continental Drift
Supporting detail Main Idea The development of Plate tectonics/ Continental Drift CONTINENTAL DRIFT * , Alfred Wegener proposed the theory of “ CONTINENTAL DRIFT” *Continents had once been joined into one landmass PANGAEA (all of the continents had been joined together)

3 *Evidence for Pangea A. Fossils -discovered fossils in eastern S. America and matching fossils in western Africa B. Geology Land features – mountain ranges in S. America line up with mountain ranges in Africa rocks layers in the Appalachian mountains of N. America match rock layers in Scotland deep scratches in rocks showed that glaciers in South Africa showed Africa was close to the S. Pole C. Puzzle pieces – Continents fit together like a puzzle Pangea

4 D. Alfred Wegener's idea of “Continental Drift” was NOT accepted
E. Wegener could NOT provide evidence for how the continents had moved 2. Great Global Rift is discovered A. 1925, Germany spent two years systematically and scientifically mapped deep sea topography and the first to reveal the extent of the sea floor's rugged terrain. B. The expedition also found that a continuous mountain-like ridge runs through the Atlantic to the southwest of Africa.. C. This ridge is now called the MID-OCEAN RIDGE

5 MID OCEAN RIDGE Use Changing Earth In your notes pages 16 and 17
Section titled “Evidence from the Sea Floor” In your notes Define MID OCEAN RIDGE with A Circle Map On ocean floor MID OCEAN RIDGE Under water mountain range

6 3. Harry Hess discovers how the plates move
Seafloor spreading Along the mid ocean ridge Cracks open up allowing magma from the mantle to come through The Magma cools, and hardens into rock and forms more crust Nemo Explorer Mantle rising through crack in sea/ocean floor allowing new rock to be made and old rock to be pushed away

7 Sea floor spreading

8 SEA- FLOOR SPREADING Use Changing Earth In your notes pages 16 and 17
Section titled “Evidence from the Sea Floor” In your notes Define SEA-FLOOR SPREADING with A Circle Map Molten magma from Mantle rises and cools SEA- FLOOR SPREADING Pushes old sea Floor away Cools and forms NEW ocean crust

9 Brace map shows the parts of the Theory of Plate Tectonics
1. Began with theory of Continental Drift 2. Discovery of Mid-Ocean Ridge Theory of Plate Tectonics 3. Discovery of the Sea- Floor Spreading process 4. Convection currents in Mantle

10 A “Flow Map" shows the Development of the THEORY OF PLATE TECTONICS
Alfred Wegener develops Idea of Continental Drift Harry Hess explains The Process of Sea Floor Spreading 1950 Convection currents, ridge push, And Slab pull Abt. 1965 The Mid Ocean Ridge is discovered 1925 Theory of Plate Tectonics

11 Continental Drift & Theory of Plate Tectonics
Multi-flow maps show cause and effect Causes Effects Mountains Continental Drift & Theory of Plate Tectonics Convection Currents in the asthenosphere Volcanoes Earthquakes

12 The Earth 100,000 million years from now

13 Review boundary Boundary = a border Lithospheric plates are not plates
3. Lithospheric/Tectonic Plate = a moving slab (large piece of land) that moves on the mantle in the asthenosphere Convection currents

14 review 4 Convection currents the flow of a liquid or gas (air) from heat Air is cooled Cool air settles to be heated again by candle Hot candle heats air Warm air rises

15 Evidence use to support Continental Drift and Plate Tectonics
1-Continental Drift Theory (all parts that Wegener proposed) 2- Evidence for activity along plate margins: 1- Earthquakes are concentrated along all three types of plate boundaries, 2- Volcanoes on the continents occur close to subduction zones. 3. Convection currents cause sea floor spreading: and the making of new oceanic crust at mid-oceanic ridges CONTINENTAL DRIFT 1.-The good geometrical fit of the continents, (puzzle pieces). 2- Geological evidence: similar rock types and structures were found on different continents that seem to fit Ancient climatic evidence: Rocks formations and markings that once formed by the movement of ice sheets (glacial deposits) occur in present 3- The occurrence of identical fossils on widely separated land masses or continents.

16 Puzzle pieces Plate Tectonics Geological evidence Fossil evidence
Plate boundaries Identifiec by earthquakes & volcanoes CONTINENTAL DRIFT Plate Tectonics Puzzle pieces Geological evidence Fossil evidence Convection currents Cause mid-ocean ridges & sea floor spreading

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