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Plate Tectonics: Earth's Dynamic Surface

Explore the theory of plate tectonics and how it explains the movement of Earth's continents, the formation of mountains, and the occurrence of earthquakes and volcanoes. Discover the forces that shape our planet's surface over time.

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Plate Tectonics: Earth's Dynamic Surface

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  1. Chapter Introduction Lesson 1 Plate Tectonics Lesson 2 Earthquakes and Volcanoes Lesson 3Weathering, Erosion, and Deposition Chapter Wrap-Up Chapter Menu

  2. How do natural processes change Earth’s surface over time? Chapter Introduction

  3. What do you think? Before you begin, decide if you agree or disagree with each of these statements. As you view this presentation, see if you change your mind about any of the statements. Chapter Introduction

  4. 1. Continents do not move. 2. Earth’s mantle is liquid. 3. Earthquakes occur and volcanoes erupt only near plate boundaries. 4. Volcanoes erupt melted rock. Do you agree or disagree? Chapter Introduction

  5. 5. Rocks cannot change. 6. Sediment can be transported by water, wind, and ice. Do you agree or disagree? Chapter Introduction

  6. Plate Tectonics • What is the theory of plate tectonics? • What evidence do scientists use to support the theory of plate tectonics? • How do the forces created by plate motion change Earth’s surface? Lesson 1 Reading Guide - KC

  7. Plate Tectonics • transform boundary • subduction zone • compression • tension • shear • plate tectonics • continental drift • convergent boundary • divergent boundary Lesson 1 Reading Guide - Vocab

  8. Plate Motion • The theory of plate tectonics states that Earth’s crust is broken into rigid plates that move slowly over Earth’s surface. • The rigid plates are called tectonic plates. • North America is part of the North American Plate. Lesson 1-1

  9. Plate Motion(cont.) • The movement of one plate is described as either moving away from or toward another plate, or sliding past another plate. • Plates move at speeds of only a few centimeters per year. • At this rate, it takes moving plates millions of years to make new continents, new mountain ranges, or other landforms. Lesson 1-1

  10. Plate Motion(cont.) What is the theory of plate tectonics? Lesson 1-1

  11. Plate Motion(cont.) Long before geologists proposed the theory of plate tectonics, they discovered evidence of continental movement. Photo by G.K. Gilbert, U.S. Geological Survey Lesson 1-1

  12. Plate Motion(cont.) • In 1912, Alfred Wegener developed the hypothesis that continents move, called continental drift. • One piece of evidence is the shape of Earth’s continents. Lesson 1-1

  13. Plate Motion(cont.) Fossil and rock evidence from the Gondwana continents also supports the hypothesis of continental drift. Lesson 1-1

  14. Geologists have discovered the same types of fossils on continents that are now separated by vast oceans. Lesson 1-1

  15. Plate Motion(cont.) What evidence do scientists use to support the theory of plate tectonics? Lesson 1-1

  16. Plate Motion(cont.) • Convection affects the mantle underneath tectonic plates. • Hotter mantle rises toward Earth’s surface and cooler mantle sinks deeper into the mantle. Lesson 1-1

  17. Plate Motion(cont.) As the Earth’s mantle moves, it pushes and pulls tectonic plates over Earth’s surface. Lesson 1-1

  18. Tectonic Plate Boundaries • The edges of tectonic plates are called plate boundaries. • A convergent boundary is where two plates move toward each other. • A divergentboundary is where two plates move apart from each other. • A transformboundary is where plates slide horizontally past each other. Lesson 1-2

  19. When two plates come together, the denser oceanic plate usually is forced down into the mantle and the less dense continental plate remains on Earth’s surface. • The area where one plate slides under another is called a subduction zone. Lesson 1-2

  20. Tectonic Plate Boundaries(cont.) • When two continents collide at a plate boundary, both continents remain on the surface. • As two continents push together, the crust rises up and large mountains form. Lesson 1-2

  21. Tectonic Plate Boundaries(cont.) • When plates move apart at divergent boundaries, a rift forms between the two plates. • A rift can form within continents when continental crust moves in opposite directions. Lesson 1-2

  22. Tectonic Plate Boundaries(cont.) • A rift also can form at divergent boundaries on the ocean floor. • As plates separate, molten rock can erupt from the rift. • As the molten rock cools, it forms new crust. Lesson 1-2

  23. Tectonic Plate Boundaries(cont.) • Tectonic plates slide past each other at transform boundaries. • The two sides of the boundary move in opposite directions. • This can deform or break features such as fences, railways, or roads that cross the boundary. Lesson 1-2

  24. Tectonic Plate Boundaries(cont.) transform Science Use horizontal relative motion Common Use to change Lesson 1-2

  25. Forces Changing Earth’s Surface • Forces within Earth cause plates to move. • The three types of plate boundaries experience different types of forces. Lesson 1-3

  26. The squeezing force at a convergent boundary is calledcompression. • The pulling force at a divergent boundary is called tension. • The side-by-side dragging force at transform boundaries is called shear. Lesson 1-3

  27. Forces Changing Earth’s Surface(cont.) • Even though plates move slowly, the forces at plate boundaries are strong enough to form huge mountains and powerful earthquakes. • Tensional forces pull the land apart and form rift valleys and mid-ocean ridges. • Compressional forces form mountains. Lesson 1-3

  28. Forces Changing Earth’s Surface(cont.) How do the forces created byplate motion change Earth’s surface? Lesson 1-4

  29. Evidence of continental drift includes fossils, mountain ranges, rock types, and the shapes of continents. • Earth’s crust is broken into pieces called tectonic plates. Convection currents in the mantle cause the plates to move. Lesson 1 - VS

  30. There are three types of tectonic plate boundaries. Movement occurs at all three boundaries. Lesson 1 - VS

  31. Which boundary is between two plates moving toward each other? A. convergent B. divergent C. subduction D. transform Lesson 1 – LR1

  32. Which zone describes the boundary where one plate slides under another plate? A. convergent B. divergent C. subduction D. transform Lesson 1 – LR2

  33. Which is the side-by-side dragging force at transform boundaries? A. shear B. tension C. compression D. continental drift Lesson 1 – LR3

  34. 1. Continents do not move. 2. Earth’s mantle is liquid. Do you agree or disagree? Lesson 1 - Now

  35. Earthquakes and Volcanoes • What causes earthquakes? • What causes volcanoes to form? • How do earthquakes and volcanoes change Earth’s surface? Lesson 2 Reading Guide - KC

  36. Earthquakes and Volcanoes • lava flow • volcanic ash • caldera • earthquake • fault • mid-ocean ridge • hot spot Lesson 2 Reading Guide - Vocab

  37. Earthquakes • Because tectonic plates move very slowly, most changes to Earth’s surface take a long time. • But some changes occur very quickly and violently. Lesson 2-1

  38. An earthquake is the rupture and sudden movement of rocks along a break or a crack in Earth’s crust. Dr. Roger Hutchinson/NOAA Lesson 2-1

  39. Earthquakes(cont.) • The surface along which the crust moves is called a fault. • When pieces of crust slide past each other, energy is released, causing the ground to shake. Photograph by N.J. Silberling, USGS Photo Library, Denver, CO Lesson 2-1

  40. Earthquakes(cont.) What causes earthquakes? Lesson 2-1

  41. Most earthquakes occur near plate boundaries, though some occur very far from plate boundaries. Lesson 2-1

  42. Earthquakes(cont.) • Compression and tension forces produce ridges and mountains as Earth’s crust moves vertically. • Liquefaction refers to when extreme shaking causes ground that is made up of loose sediment to behave more like a liquid than a solid. • Earthquakes can trigger landslides, which bring rocks and soil from the tops of mountains into valleys. Lesson 2-1

  43. Earthquakes(cont.) Earthquakes that happen underwater can cause tsunamis—huge ocean waves created by movement at a fault. Lesson 2-1

  44. Earthquakes(cont.) How do earthquakes change Earth’s surface? Lesson 2-1

  45. Volcanoes • Volcanoes are landforms that form when magma erupts onto Earth’s surface as lava. • Volcanoes can occur at divergent and convergent plate boundaries and at hot spots. Lesson 2-2

  46. The mountains that form as lava from a volcano at a divergent boundary builds up and cools are called mid-ocean ridges. Lesson 2-2

  47. At some convergent boundaries, one tectonic plate sinks, melts the mantle, and forms magma that erupts onto the plate that does not sink. Lesson 2-2

  48. Volcanoes (cont.) • Hot spots are locations where volcanoes form far from plate boundaries. • The Hawaiian Islands in the middle of the Pacific Ocean and Yellowstone National Park in Wyoming are hot spots. Lesson 2-2

  49. Volcanoes (cont.) • Because magma is hot, it is also less dense than the rock material around it. • Rising magma and great pressure caused by dissolved gases eventually erupt through cracks in Earth’s surface, creating a volcano. Lesson 2-3

  50. Most of Earth’s largest volcanoes are located at convergent plate boundaries. Lesson 2-3

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