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Plate Tectonics Introduction

Plate Tectonics Introduction. Chapter 9. Earth’s Structure. Earth’s interior consists of three major zones defined by its chemical composition: Crust Mantle Core. Crust. Thin, rocky outer layer of Earth Divided into continental and oceanic Continental crust is about 5-47 miles thick

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Plate Tectonics Introduction

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  1. Plate Tectonics Introduction Chapter 9

  2. Earth’s Structure • Earth’s interior consists of three major zones defined by its chemical composition: • Crust • Mantle • Core

  3. Crust • Thin, rocky outer layer of Earth • Divided into continental and oceanic • Continental crust is about 5-47 miles thick • Consists of many rock types • Oceanic crust is about 4 miles thick • Composed of igneous rocks • Crust and upper most part of the mantle make up the lithosphere

  4. Mantle • Solid, rocky shell that extends to a depth of about 1800 miles • Upper Mantle: • Lithosphere • Rigid • Asthenosphere • Soft, flexible • Lower Mantle

  5. Core • Sphere composed of iron-nickel alloy • Outer core • Liquid layer is about 1400 miles thick • Earth’s magnetic field is generated from the flow of metallic iron • Inner core • Radius of about 760 miles • Due to the extreme pressure, the material is solid

  6. Continental Drift Hypothesis • A German scientist and meteorologist, Alfred Wegener, proposed a hypotheses: • The continents had once been joined to form a single supercontinent, Pangaea • Pangaea meaning all land

  7. Continental Drift Evidence • The Continental Puzzle • Similar coastlines on opposite sides of the ocean • Continents fit together, like a puzzle • Matching Fossils • Fossil organisms found on different landmasses • Rock Types and Structures • Several mountain belts end at one coastline and reappear on a landmass across the ocean • Appalachian Mountains in US, ending off the coast of Newfoundland (Figure 4 on page 251) • Ancient Climates • Glacier evidence, Figure 5 on page 252

  8. Matching Mountain Ranges

  9. Glacier Evidence

  10. A New Theory Emerges… • Wegener could not provide an explanation of exactly what made the continents move • Data on earthquake activity and Earth’s magnetic field became available • By 1968, these findings led to a new theory, plate tectonics

  11. Plate Tectonics Theory • The upper most mantle and crust, behave as a strong, rigid layer known as the lithosphere • Lithosphere is divided into plates, which move and continually change shape and size • 7 major plates (pages 256-257, Figure 8) • The grinding movements of the plates generate earthquakes, create volcanoes and deform masses of rock into mountains

  12. Plate Boundaries • Convergent • Two plates move together • Divergent • Two plates move apart • Transform (fault) • Two plates slide past each other

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