1. Plate Tectonics V205.03

2. GCS SciVis Plate Tectonics

3. GCS SciVis What is Plate Tectonics The Earth is broken into large Plates. The size and position of Plates change. Plate edges colliding - geologic activity Cause of Earthquakes & Volcanoes Creates Mountains Deep ocean vents – site of creation of life

4. GCS SciVis Earth has 3 Layers Core Mantle Crust

5. GCS SciVis Outer Layers of the Earth The Lithosphere (Greek, Lithos for Stone) is the rigid, outermost layer of outer crust and uppermost mantle. This makes up the “Plate” of Plate Tectonics.

6. GCS SciVis Asthenosphere The Asthenosphere is the solid part of the mantle that “Flows” in a process called plastic behavior. Plastic behavior is much like toothpaste moving in a tube.

7. GCS SciVis Continental Drift Continental Drift theory was proposed by Alfred Wegener in 1912. He used continental fit, distribution of fossils, ancient climates, and the wandering of Earth's polar regions to support his Theory. He stated the present continents were part of a super continent – Pangaea.

8. GCS SciVis Pangaea

9. Sea-Floor Spreading

10. GCS SciVis Sea-Floor Spreading Harry Hess proposed that new ocean floor is formed at the rift of mid-ocean ridges. The ocean floor, and the rock beneath it, are produced by magma that rises from deeper levels. Hess suggested that the ocean floor moved laterally away from the ridge and plunged into an oceanic trench along the continental margin.

11. GCS SciVis Subduction As new ocean floor is created by sea-floor spreading at the mid- oceanic ridges it is consumed at the subduction zones where the lithosphere sinks under the asthenosphere.

12. GCS SciVis Convergent Boundaries Oceanic-Continental Convergence Continent-Continent Convergence Oceanic-Oceanic Convergence

13. GCS SciVis Oceanic-Continental Convergence When the leading edge of an oceanic crust collides with continental crust. Oceanic crust is denser – it is subducted, or forced under the less dense continental crust. A deep oceanic trench forms along a subduction zone.

14. GCS SciVis Continent-Continent Convergence When two leading edges of continental crust collide. Neither crust is conducted – they have the same density. Colliding edges are crumpled and uplifted, producing mountains.

15. GCS SciVis Oceanic-Oceanic Convergence A collision between oceanic crust and another oceanic crust. A deep ocean trench forms when one of the oceanic crust is subducted. Part of the subducted crust melts to form magma. Molten magma rise to form volcanic islands.

16. GCS SciVis Convergent Boundaries Places where plates crash or crunch into each other. All the folding and bending makes rock in both plates break and slip, causing earthquakes. Rock deep in the Earth melts, builds up pressure causing volcanoes.

17. GCS SciVis Continental Crush An ocean floor will always slide under the land mass. This is because the land mass is more buoyant, or lighter, than the ocean floor. When two land masses meet neither will slide under the other. Instead, the two crush together at what is known as a collisional boundary. They crumple and fold. Some pieces of land are thrust over or under other pieces. The result is a mountain range.

18. GCS SciVis Divergent Boundaries Places where plates come apart are called divergent boundaries. When Earth's brittle surface layer is pulled apart, it breaks along parallel faults that tilt slightly outward from each other. As the plates separate along the boundary, the block between the faults cracks and drops down into the soft, plastic interior. The sinking of the block forms a central valley called a rift. Magma (liquid rock) seeps upward to fill the cracks. In this way, new crust is formed along the boundary.

19. GCS SciVis Divergent Boundaries

20. GCS SciVis Transform Boundaries Places where plates slide past each other are called transform boundaries. The most famous transform boundary in the world is the San Andreas fault. Los Angeles will not crack off and fall into the ocean as popularly thought, but it will simply creep towards San Francisco at about 6 centimeters per year. In 16 million years, the plates will have moved so much that Los Angeles will be north of San Francisco!

21. GCS SciVis Transform Boundaries

22. GCS SciVis Summary Illustration

23. GCS SciVis

24. Measuring Plate Movement Global Positioning System (GPS) is a constellation of 24 satellites which are used for navigation and precise geodetic position measurements. They can also be used to plot global velocities.

25. GCS SciVis Measuring Plate Movement Satellite Laser Ranging (SLR) determines round- trip time of light from ground-based lasers at widely separated points on the earth to mirrors on satellites.

26. GCS SciVis Measuring Plate Movement Very Long Baseline Interferometry (VLBI) uses the difference in time at widely separated places of received quasar-emitted radio signals and can also be used to obtain plate movement.VLBI

27. GCS SciVis Measuring Plate Movement Volcanic and earthquake activity can also be measured to help determine plate movement. The “Ring of Fire” (area of volcanic activity) in the Pacific Ocean helped map out certain oceanic plates.

28. GCS SciVis The End