1 / 26

4.5 The Theory of Plate Tectonics

Learn the theory of plate tectonics, including the three types of plate boundaries: transform, divergent, and convergent. Discover how plates move and the effects of their movement. Engage in hands-on activities to visualize plate boundaries.

ssmead
Download Presentation

4.5 The Theory of Plate Tectonics

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. 4.5 The Theory of Plate Tectonics

  2. Objectives • Explain the theory of plate tectonics • Describe the three types of plate boundaries.

  3. Engage/Explore • What is a plate? • Think of other contexts in which the word is used. • Metal plates that cover machinery • Home plate in baseball, • a reptile’s plates or scales • plate of photographs in a textbook

  4. Introduction • J. Tuzo Wilson - Canadian scientist. • He discovered that there are cracks in the continents similar to those on the ocean floor.

  5. Wilson proposed that the lithosphere is broken into separate sections called plates. • Plates can carry both continents or parts of the ocean floor.

  6. Great Rift Valley in East Africa

  7. A Theory of Plate Motion • Wilson combined the thoughts of sea-floor spreading, Earth’s plates, and continental drift into a theory. • A scientific theory is a well-tested concept that explains a wide range of observations.

  8. Plate tectonics is the geological theory that state that pieces of Earth’s lithosphere are in constant, slow motion, driven by convection currents in the mantle. It explains the formation, movement, and subduction of Earth’s plates.

  9. How can Earth’s plates move? • The plates of the lithosphere float on top of the asthenosphere. Convection currents rise in the asthenosphere and spread out beneath the lithosphere.

  10. Earth’s Lithospheric Plates

  11. Collide Pull apart Grind past each other Volcanoes Mountain ranges Deep-sea trenches Affects of the plates

  12. Earth’s Lithospheric Plates • Which plates include only ocean floor? • Which plates include both continents and ocean floor?

  13. Plate Boundaries • Demonstration • Materials - 2 woooden blocks • Three types of blocks 1. Transform boundary - slide past 2. Divergent boundary - pull away 3. Convergent boundary - push two blocks together. • Draw the blocks with labels and arrows showing the direction of each block’s movement.

  14. Block demonstration • Demonstrate the boundaries using blocks. • Why do you think earthquakes occur frequently at transform boundaries? • Answer: The plates cannot move smoothly past one another because of the irregular nature of faults. • How fast do you think Earth’s plates are moving? • Answer: Only a few centimenters per year.

  15. Plate Boundaries • Faults - breaks the Earth’s crust where rocks have slipped past each other which form along these boundaries. • Three kinds of boundaries 1. Transform boundary - slide past 2. Divergent boundary - pull away 3. Convergent boundary - push two blocks together.

  16. Transform Boundary • A place where two plates slip past each other, moving in opposite directions. • Earthquakes occur along these boundaries. • San Andreas Fault is an example. The Pacific plate is sliding past the North American plate. • Crust is neither created nor destroyed.

  17. San Andreas Fault

  18. San Andreas Fault

  19. Divergent Boundary • The place where two plates move apart. • Most occur at the mid-ocean ridge and on land. • The boundary forms rift valleys. • Example - Great Rift Valley has a 3000 km crack.

  20. Rio Grande Rift • Extends from central Colorado to El Paso, Texas.

  21. Exploring Exercise - Plate Tectonics Plate Tectonics What is magma? What is the magma coming from that is shown erupting through the mid-ocean ridge and the rift valley? Answer: asthenosphere What new process are shown?

  22. Convergent Boundaries • Two plates come together. This is called a collision • When two continental plates collide, why isn’t one subducted beneath the other? Appalachian Mountains formed when two continental plates collided. -The density of plates determines which plate comes out on top.

  23. Appalachian Mountains

  24. Appalachian Mountains

  25. Convergent Boundaries

  26. The Continents’ Slow Dance • The continents move at slow rates: one to ten centimeters per year. • Pangea began to drift apart about 225 million years ago.

More Related