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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 1.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 ) Main Idea Supporting detail

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

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

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

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

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

12 The Earth 100,000 million years from now

13 Review 1.Boundary = a border 2.Lithospheric plates are not plates 3. Lithospheric/Tectonic Plate = a moving slab (large piece of land) that moves on the mantle in the asthenosphere 2.Convection currents boundary

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

15 Evidence use to support Continental Drift and Plate Tectonics 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. 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

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

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