Chapter 1: Plate Tectonics

1. Chapter 1: Plate Tectonics Earth’s Interior Convection and the Mantle Drifting Continents Sea-Floor Spreading The Theory of Plate Tectonics

2. F.1.1.1 Explain how geologists learn about Earth’s inner structure. F.1.1.2 Identify the characteristics of Earth’s crust, mantle, and core. Earth’s Interior

3. Geologists have used two main types of evidence to learn about Earth’s interior: direct evidence from rock samples and indirect evidence from seismic waves. Rocks from inside Earth give geologists clues about Earth’s structure. Using data from seismic waves produced by earthquakes, geologists have learned Earth’s interior is made up of several layers. Earth’s Interior

4. Earth’s Interior

5. The crust is the layer of rock that forms Earth’s outer skin. The crust is a layer of solid rock that includes both dry land and the ocean floor. Oceanic crusts consists mostly of rocks such as basalt. Continental Crust, is mostly made up of granite. Earth’s Interior

6. The Mantle is a layer of hot rock. Earth’s mantle is made up of rock that is very hot, but solid. Scientists divide the mantle into layers based on the physical characteristics of those layers. The uppermost part of the mantle and the crust together form a rigid layer called the lithosphere. Below the lithosphere is a soft layer called the asthenosphere. Beneath the asthenosphere, the mantle is solid. Earth’s Interior

7. The core is made mostly of the metals iron and nickel. It consists of two parts – a liquid outer core and a solid inner core. The outer core is a layer of molten metal that surround the inner core. The inner core is a dense ball of solid metal. Scientists think that movements in the liquid outer core create Earth’s magnetic field. Because Earth has a magnetic field, the planet acts like a giant bar magnet. (Keeps us in orbit) Earth’s Interior

8. F.1.2.1 Explain how heat is transferred. F.1.2.2 Identify what causes convection currents. F.1.2.3 Describe convection currents in Earth’s mantle. Convection and the Mantle

9. There are three types of heat transfer: radiation, conduction, and convection. Convection and the Mantle

10. Radiation is the transfer of energy through empty space. Sunlight warming Earth’s surface, or a microwave. Convection and the Mantle

11. Conduction is heat transfer by direct contact of particles of matter. Convection and the Mantle

12. Convection is the transfer of heat by the movement of a heated fluid. Convection and the Mantle

13. The flow that transfers heat within a fluid is called a convection current. The heating and cooling of the fluid, changes in the fluid’s density, and the force of gravity combine to set convection currents in motion. Convection currents flow in the mantle. The heat source for these currents is heat from Earth’s core and from the mantle itself. Convection and the Mantle

14. Convection and the Mantle

15. F.1.3.1 Explain Alfred Wegener’s hypothesis about the continents. • F.1.3.2 List the evidence used by Wegener to support his hypothesis. • F.1.3.3 Explain why other scientists of Wegener’s time rejected his hypothesis. Drifting Continents

16. Alfred Wegener wondered why the coasts of several continents matched so well. • Wegener’s hypothesis was that all the continents had once been joined together in a single landmass and have since drifted apart. The Super-continent was named Pangaea – “all lands”. • Pangaea existed 300 million years ago, and over tens of millions of years, Pangaea broke apart and drifted to their present-day locations, becoming the seven continents today: North America, South America, Africa, Australia, Antarctica, Europe, and Asia. Drifting Continents

17. Drifting Continents

18. Drifting Continents

19. Simulation of moving plates: http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Continents.shtml Drifting Continents

20. The idea that the continents slowly moved over Earth’s Surface became known as the continental drift. Wegener presented evidence to support his theory: • Mountain Ranges and landforms provide evidence for continental drift. Mountain ranges in South America and Africa line up. Also, European coal fields match with similar coal fields in North America. We know coal is a product of once living, animals and plants. Drifting Continents

21. Evidence from Fossils: Fossils of the plant Glossopteris has been found in rocks on widely separated landmasses. Additionally, fossils of the reptiles Mesosaurus and Lystrosaurus also have been found on widely separated landmasses. • Evidence from the Climate: An island in e Artic Ocean contains fossils of tropical plants. The island at one time must have been close to the equator. Also, scratches in rocks made by glaciers have been found in South Africa. Wegener stated Earth’s climate has not changes, but the positions of the continents have changed. Drifting Continents

22. Wegener could not provide a satisfactory explanation for the force that pushes or pulls the continents. Most geologists rejected his theory. Due to new evidence, Wegener’s theory is being reconsidered. Drifting Continents

23. F.1.4.1 What is the process of sea-floor spreading? • F.1.4.2 What is the evidence for sea-floor spreading? • F.1.4.3 What happens at deep-ocean trenches? Sea-Floor Spreading

24. Scientists mapped the mid-ocean ridge using sonar. • Mid-Ocean ridge is the longest chain of mountains in the world, curving along the sea floor of all Earth’s oceans. • Sonar is a device that bounces sound waves off underwater objects and then records echoes of these sound waves. Sea Floor Spreading

25. Earth’s ocean floors move like a conveyor belt, carrying the continents with them. This movement begins at the mid-ocean ridge. The ridge forms along a crack in the oceanic crust. At the mid-ocean ridge, molten material rises from the mantle and erupts. The molten material then spreads out, pushing older rock to both sides of the ridge. Sea Floor Spreading

26. Then more molten material splits apart the strip of rock, pushing it aside. This process, called sea-floor spreading, continually adds new material to the ocean floor. Sea Floor Spreading

27. Sea-floor spreading

28. Scientists have found strange rocks shaped like pillows in the central valley of the mid-ocean ridge. Such rocks can form only if molten material hardens quickly after erupting under water. • Scientists discovered that the rock that makes up the ocean floor lies in a pattern of magnetized strips. • Lastly, the last piece of evidence came from rock samples, the farther from the ridge the rocks were taken, the older they were. Evidence

29. http://kids.earth.nasa.gov/archive/pangaea/evidence.html Evidence – Further Reading

30. The ocean floor does not just keep spreading, it also sinks beneath deep underwater canyons called deep-ocean trenches. • Where there are trenches, subduction takes place. Subduction is the process by which the ocean floor sinks beneath a deep-ocean trench and back into the mantle. This happens over tens of millions of years. Sea Floor Spreading

31. The process of subduction and sea-floor spreading can change the size and shape of the oceans. Because of these processes, the ocean floor is renewed about every 200 million years. • The Pacific Ocean is shrinking. • The Atlantic Ocean is expanding. Sea-Floor Spreading

32. F.1.5.1 Explain the theory of plate tectonics • F.1.5.2 Describe the three types of plate tectonics. The Theory of Plate Tectonics

33. Earth’s lithosphere is broken into separate sections called plates. The plates fit closely together along cracks in the crust. Theory of Plate Tectonics

34. The Theory of Plate Tectonics

35. Plate Tectonics is the geological theory that states pieces of the Earth’s lithosphere are in constant, slow motion, driven by convection currents in the mantle. The theory of plate tectonics explains the formation, movement, and subduction of Earth’s plates. The Theory of Plate Tectonics

36. Two plates move apart – these occur mostly at the mid-ocean ridge. (creation of valleys) Divergent Boundary

37. Divergent Boundary

38. Two plates come together causing a collision. Convergent Boundary

39. Convergent

40. A place where two plates slip past each other, moving in opposite directions. Earthquakes occur frequently along these boundaries. Transform Boundary

41. The LAGEOS II satellite, built by the Italian Space Agency, AgenziaSpazialeItaliana (ASI), and managed by NASA's Goddard Space Flight Center, measures crustal movement by using Satellite Laser Ranging technology Today – NASA’s Role

42. Residents of warm southern California are moving to Alaska whether they like it or not. Scientists, using the theory of plate tectonics, say that southern California is moving north and will collide with Alaska in approximately 150 million years. Today

43. What can scientists predict about some of the features of the Earth existing today? Quite a lot. The Atlantic Ocean will continue to expand, while the Pacific Ocean (originally Panthalassa Ocean) will shrink. Eventually, the Mediterranean Sea (remnant from the Tethys Sea) will disappear, connecting Africa with Europe. India will continue to push into the southern Asian continent, pushing the Himalayas higher. Meanwhile the city of Los Angles will continue its journey north to join with the city of San Francisco. This will take several million years to occur. Maybe in another 200 million years there will be no need for a transoceanic trip from America to Asia. Predictions for the Future:

44. Lab: Mapping a future world or modeling plate boundaries • Review Prep – Chapter One • Review (1-10) page • Test Prep (Terra Nova) 1-5 • Review Sheet • Review for Chapter One • Chapter One Assessment Chapter one – plate tectonics