1 / 38

Earth Science, 10e

Earth Science, 10e. Edward J. Tarbuck & Frederick K. Lutgens . Plate Tectonics Chapter 7. Earth Science, 10e Stan Hatfield and Ken Pinzke Southwestern Illinois College. Continental drift: an idea before its time . Alfred Wegener First proposed hypothesis, 1915

sovann
Download Presentation

Earth Science, 10e

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Earth Science, 10e Edward J. Tarbuck & Frederick K. Lutgens

  2. Plate TectonicsChapter 7 Earth Science, 10e Stan Hatfield and Ken Pinzke Southwestern Illinois College

  3. Continental drift: an idea before its time • Alfred Wegener • First proposed hypothesis, 1915 • Published The Origin of Continents and Oceans • Continental drift hypothesis • Supercontinent called Pangaea began breaking apart about 200 million years ago • Continents "drifted" to present positions • Continents "broke" through the ocean crust

  4. Pangaea approximately 200 million years ago

  5. Continental drift: an idea before its time • Wegener's continental drift hypothesis • Evidence used by Wegener • Fit of South America and Africa • Fossils match across the seas • Rock types and structures match • Ancient climates • Main objection to Wegener's proposal was its inability to provide a mechanism

  6. Wegener’s matching of mountain ranges on different continents

  7. Paleoclimatic evidence for Continental Drift

  8. Plate tectonics: the new paradigm • More encompassing than continental drift • Associated with Earth's rigid outer shell • Called the lithosphere • Consists of several plates • Plates are moving slowly • Largest plate is the Pacific plate • Plates are mostly beneath the ocean

  9. Plate tectonics: the new paradigm • Asthenosphere • Exists beneath the lithosphere • Hotter and weaker than lithosphere • Allows for motion of lithosphere • Plate boundaries • All major interactions among plates occur along their boundaries

  10. Convergent: Continental to Continental Convergent plate boundaries (destructive margins) • Definition:When subducting plates contain continental material, two continents collide • How they move: two continental plates push each other up • Landform Results: new mountain ranges • Example: Himalayas • Density: Same density so they both push each other up

  11. A continental-continental convergent plate boundary

  12. The collision of India and Asia produced the Himalayas (before)

  13. The collision of India and Asia produced the Himalayas (after)

  14. Convergent Plate Boundaries: Oceanic to Continental Convergent plate boundaries (destructive margins) • Oceanic-continental convergence • Definition: an oceanic plate and continental plate colliding • How they move:oceanic plate slides underneath continental plateDenser oceanic slab sinks into the asthenosphere • Land formations: Pockets of magma develop and rise, continental volcanic arcs form, chain of volcanic islands • Examplesinclude the Andes, Cascades, and the Sierra Nevadan system

  15. An oceanic-continental convergent plate boundary

  16. Convergent Plate Boundaries: Oceanic to Oceanic • Oceanic-oceanic convergence • Definition: Two oceanic slabs converge and one descends beneath the other • How they move: Often forms volcanoes on the ocean floor • Land formation results:Volcanic island arcs forms as volcanoes emerge from the sea • Examples: include the Aleutian, Mariana, and Tonga islands, • Density: same

  17. An oceanic-oceanic convergent plate boundary

  18. Divergent Plate Boundaries Divergent plate boundaries (constructive margins) • Definition: Two plates move apart • How they move: Mantle material upwells to create new seafloor • Landform Results: Ocean ridges and seafloor spreading • Oceanic ridges develop along well-developed boundaries • Along ridges, seafloor spreading creates new seafloor • Examples: Iceland, and East Africa • Density: Same density

  19. Divergent boundaries are located mainly along oceanic ridges

  20. The East African rift – a divergent boundary on land

  21. Transform Boundaries • Definition: Plates slide past one another, horizontally (side to side) • No new crust is created • No crust is destroyed • How they move: At the time of formation, they roughly parallel the direction of plate movement • Aid the movement of oceanic crustal material • Examples: San Andres fault in California • Density: Plates have the same density

  22. Plate tectonics: the new paradigm • Evidence for the plate tectonics model • Paleomagnetism • Probably the most persuasive evidence • Ancient magnetism preserved in rocks • Paleomagnetic records show • Polar wandering (evidence that continents moved) • Earth's magnetic field reversals • Recorded in rocks as they form at oceanic ridges

  23. Apparent polar-wandering paths for Eurasia and North America

  24. Paleomagnetic reversals recorded by basalt flows at mid-ocean ridges

  25. Plate tectonics: the new paradigm • Evidence for the plate tectonics model • Earthquake patterns • Associated with plate boundaries • Deep-focus earthquakes along trenches provide a method for tracking the plate's descent • Ocean drilling • Deep Sea Drilling Project (ship: Glomar Challenger)

  26. Distribution of earthquake foci at plate boundaries

  27. Earthquake foci in the vicinity of the Japan trench

  28. Plate tectonics: the new paradigm • Evidence for the plate tectonics model • Hot spots • Rising plumes of mantle material • Volcanoes can form over them • e.g., Hawaiian Island chain • Chains of volcanoes mark plate movement

  29. Plate tectonics: the new paradigm • Evidence for the plate tectonics model • Ocean drilling • Age of deepest sediments • Youngest are near the ridges • Older are at a distance from the ridge • Ocean basins are geologically young

  30. The Hawaiian Islands have formed over a stationary hot spot

  31. Plate tectonics: the new paradigm • Measuring plate motion • By using hot spot “tracks” like those of the Hawaiian Island - Emperor Seamount chain • Using space-age technology to directly measure the relative motion of plates • Very Long Baseline Interferometry (VLBI) • Global Positioning System (GPS)

  32. Directions and rates of plate motions

  33. Plate tectonics: the new paradigm • Driving mechanism of plate tectonics • No one model explains all facets of plate tectonics • Earth's heat is the driving force • Several models have been proposed • Slab-pull and slab-push model • Descending oceanic crust pulls the plate • Elevated ridge system pushes the plate

  34. Plate tectonics: the new paradigm • Driving mechanism of plate tectonics • Several models have been proposed • Plate-mantle convection • Mantle plumes extend from mantle-core boundary and cause convection within the mantle • Models • Layering at 660 kilometers • Whole-mantle convection • Deep-layer model

  35. Layering at 660 kilometers

  36. Whole-mantle convection

  37. Deep-layer model

  38. End of Chapter 7

More Related