Chapter Ten

1. Chapter Ten PLATE TECTONICS

2. Background Information Layers of Earth • The Earth is made up of several layers that have different properties and compositions. • There are three main layers: • Crust • Mantle • Core (inner and outer)

3. Section 1: Continental Drift Evidence of Continental Drift • Alfred Wegener (German meteorologist) • Suggested that all the continents were joined together at some times in the past • 1912: he proposed the hypothesis of the continental drift which explains that continents have moved slowly to their current locations over time • Pangaea(“all land”) is the name he gave to the large land mass that he believes existed over 200 million years ago

4. Section 1: Continental Drift Evidence of Continental Drift

5. Section 1: Continental Drift Evidence of Continental Drift • Evidence of Continental Drift • Fossil • The reptile Mesosauruswas found in South America and Africa • Fossils from a fernlike plant Glossopteriswas found in Africa, Australia, South America and Antarctica • Climate • Fossils of warm weather plants were found on an island in Arctic Ocean • Glacial deposits and grooved bedrock were found on South America, Africa, India, and Australia

6. Section 1: Continental Drift Evidence of Continental Drift • Rock • Similar rock structures and types of rocks are found on different continents • Appalachian Mountains (below left) in eastern United States are similar to mountains in Greenland and Western Europe (below right) • South America and western Africa have similar rock structures

7. Section 2: Seafloor Spreading Mapping the Ocean Floor • Harry Hess (1960) • Proposed the new idea of seafloor spreading to explain how the continents could move. • Seafloor spreading is when a hot, less dense material is forced up through the Earth’s crust in an opening called a mid-ocean ridge, it turns and flows sideways, carrying the seafloor away from the ridge in both directions.

8. Section 2: Seafloor Spreading Mapping the Ocean Floor • Evidence for Seafloor Spreading: • Age evidence: • Rocks on sea floor – near mid-ocean ridge – were 180 million years old or younger • Rocks away from mid-ocean ridge – near continents – some were almost 4 billion years old • Magnetic evidence: • Scientists found that rocks on the ocean floor show many periods of magnetic reversal.

9. Section 3: Theory of Plate Tectonics Plate Tectonics • Seafloor spreading let scientists know what was happening with the crust and upper mantle. • 1960 – scientists developed a new theory that put continental drift together with seafloor spreading. • Theory of Plate Tectonics: Earth’s crust and upper mantle are broken into sections. Theses sections – called plates, move around on a layer of the mantle.

10. Section 3: Theory of Plate Tectonics Plate Tectonics • Plates are made of the crust and a part of the upper mantle. • The lithosphere is a rigid layer that is generally less dense than material that is underneath. • The plastic-like layer below the lithosphere is called the asthenosphere.

11. Section 3: Theory of Plate Tectonics Plate Boundaries • 3 kinds of plate boundaries: • Divergent Boundary: boundary between plates that are moving apart

12. Section 3: Theory of Plate Tectonics Plate Boundaries • 3 kinds of plate boundaries: • Convergent Boundary: Boundary between plates that are moving together • Area where one plate goes down into the mantle is called the sub-ductionzone. • Volcanoes usually form near convergent boundaries when the rock melts or mountains can form when two plates collide and crumple up.

13. Section 3: Theory of Plate Tectonics Plate Boundaries • 3 kinds of plate boundaries: • Transform Boundary: boundary where plates are sliding past each other.

14. Section 3: Theory of Plate Tectonics Causes of Plate Tectonics • Process of heating and cooling, which causes movement of particles is called convection current. • Effects of Plate Tectonics: • Plates are constantly interacting with other plates. • Forms mountain ranges, volcanoes, faults, rift valleys