EARTH S INTERIOR, EVIDENCE FOR PLATE TECTONICS AND PLATE BOUNDARIES

Transcription

1 EARTH S INTERIOR, EVIDENCE FOR PLATE TECTONICS AND PLATE BOUNDARIES

2 LAYERS OF THE EARTH Crust Inner Core Most Dense Solid Iron & Nickel Mantle Thickest layer Outer Core Liquid Iron & Nickel

3 ANOTHER LOOK AT THE EARTH

4 Plate Tectonics Theory The lithosphere is broken into separate sections called plates. The geological theory that states that pieces of Earth s lithosphere are in constant, slow motion, driven by convection currents in the mantle.

5 Continental Drift ess.earthsys.wegener1/plate-tectonics-the-scientistbehind-the-theory/ Alfred Wegener Click Below (may not see link) click below Alfred Wegener first proposed the theory of continental drift. Continental drift is Wegener s theory that all continents had once been joined together in a single landmass and have drifted apart since. Wegener named this supercontinent Pangaea. Wegener s theory was rejected by scientists because he could not explain what force pushes or pulls the continents.

6 Evidence for Continental Drift and Plate Tectonics 1. Apparent "fit" of the continents They look like they fit together, this caused the first investigations and hypothesizing 2. Fossil Evidence Fossil reptile, Mesosaurus, found in South America and Africa Fossil fern, Glossopteris, found in Africa, Australia, India, South America, and Antarctica 3. Rock and Glacial Evidence a. Matching rocks and mountain ranges in South America and Africa 1) Appalachian rocks in North America, Greenland and western Europe 2) Mountain range in South America and Africa appears split, rocks and features match b. Ancient glacial features match in South America, Africa, India, and Australia

7 4. Sea Floor Evidence (after Wegener) Mid-Ocean Ridge System- the longest feature on the crust of the Earth, ~50000 km like the seam of a baseball, mirrors the shape of the coastlines Examples: a. Rocks are youngest at the center (rift zone), become older as you move away from the center b. The ocean floor is much younger than the continents, Oldest ocean floor rocks 160 million years & oldest continental rocks are about 4 billion years old 5. Now with GPS satellites we can actually measure the movement.

8 SEAFLOOR SPREADING IS THE PROCESS THAT CONTINUALLY ADDS NEW MATERIAL TO THE OCEAN FLOOR. THIS HAPPENS AT THE MID-OCEAN RIDGES.

9 The ocean floor plunges into deep underwater canyons called trenches. Subduction takes place in trenches. Subduction is the process by which the ocean floor sinks beneath a trench and back into the mantle.

10 PLATES AND PLATE MOTION Plates: large sections of the Earth s lithosphere that slowly move on the surface of the Earth Lithosphere: the solid crust and upper mantle Slowly: 1 to 10 cm per year Asthenosphere: the layer of the upper mantle that is able to slowly move over time because it has the property of plasticity Plasticity: the ability of a solid to behave like a liquid Such as flow slowly Movement /Flowing because of convection currents Currents that move because of differences in density Warm less dense material rises Cool more dense material sinks

11 THE DRIVING FORCE FOR PLATE TECTONICS IS CONVECTION CURRENTS IN THE MANTLE OF THE EARTH. THIS IS ONE THING WEGENER DID NOT KNOW.

12 Plate Boundaries

13 PLATE BOUNDARIES Divergent Boundary Where the warm mantle and heated crustal material rises Mid-ocean ridges Mid-continent rift zones- only for a while then forms a mid-ocean ridge

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15 PLATE BOUNDARIES Ocean-Continent Convergent Boundary

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17 PLATE BOUNDARIES Ocean-Ocean Convergent Boundary

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19 PLATE BOUNDARIES Continent-continent Convergent Boundary

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22 PLATE BOUNDARIES Transform fault Boundary

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24 HOT SPOTS There are some places on Earth where hot molten material rises to the surface not related to plate tectonics- hot spots Hawaii- in the middle of the Pacific Plate Shows movement over time of the Pacific Plate Yellowstone National Park- the location of a supervolcano

25 PLATE BOUNDARIES uleng/geointromod.swf

26 PLATE BOUNDARIES