Name: ______

Geology Chapter 9 – Plate Tectonics

Michael Wysession Washington University

Big Ideas Earth's lithosphere is broken into about a dozen major pieces and many other smaller pieces. These "plates" move about Earth's surface in a process called plate tectonics, which is the unifying framework within which all of modern geology is understood. Plate tectonics explains the existence of earthquakes, volcanoes, mountains, oceans, and many other things.

Space and Time Earth's plates have been moving around, by the slab-pull force and pushed by the ridge-push force. Plates that contain continents tend to move slowly. Matter and Energy Plate tectonics is the surface expression of a global cycle of mantle convection. Oceanic plates form at mid-ocean ridges, cool, and sink back into the mantle at subduction zones. The decay of radioactive isotopes is the source of heat that drives mantle convection.

Earth as a System Plate tectonics has profoundly affected the history of Earth's life: volcanic eruptions affect the atmosphere, the positions of continents affect ocean circulation, and plate collisions have created the continents and their unique distributions of minerals, metals, and other resources.

Section 1 – Continental Drift

  1. What does Wegener’s continental drift hypothesis state?
  2. What is Pangaea and what does it mean?
  3. List the four types of evidence for continental drift.
  4. Briefly describe the continental puzzle.
  5. Fossil evidence for continental drift includes several ______organisms found on ______landmasses.
  6. If the continents existed as ______, the rocks found in a particular region on one continent should ______match in ______and ______those in adjacent positions on the adjoining continent.
  7. What form does rock evidence for continental drift exist in?
  8. What kinds of climate evidence did Wegener find to support his hypothesis?
  9. Explain why Wegener’s hypothesis was rejected?
  10. What new evidence was there that led to a new theory called plate tectonics?

Section 2 – Plate Tectonics

  1. According to the ______, the uppermost mantle, along with the overlying ______, behaves as a strong, rigid layer known as the ______.
  2. What are plates?
  3. What can plates do?
  4. How fast do the plates move?
  5. What drives their movement?
  6. What does the grinding movement of Earth’s lithospheric plates generate?
  7. Name the three types of plate boundaries.
  8. When do divergent (spreading centers) boundaries occur and what do they result in?
  9. Where do convergent boundaries form and what do they result in?
  10. What are transform fault boundaries and give an example?

Section 3 – Actions at Plate Boundaries

  1. Where do most divergent plate boundaries occur and what can they be thought of?
  2. The system of ocean ridges is the longest ______feature on Earth’s surface, stretching more than ______in length.
  3. What are rift valleys?
  4. What is seafloor spreading?
  5. Name two examples of rift valleys.
  6. How do rifts begin to form?
  7. Because lithosphere is “______” at convergent boundaries, they are also called ______.
  8. Where does a subduction zone occur?
  9. When the leading edge of a continental plate converges with an oceanic plate, the ______dense continental plate remains ______. The ______oceanic slab sinks into the ______.
  10. Name an example of a continental volcanic arc.
  11. What are they produced in part by?
  12. What happens when two oceanic crusts converge?
  13. Give an example of a volcanic island arc.
  14. What is the result of the collision of two continents?
  15. Name several examples of mountain systems formed by continental-continental collisions.
  16. At ______fault boundaries, plates ______past each other without ______the lithosphere.
  17. Give an example of a transform fault that cuts through the continental crust located on the West Coast.

Section 4 – Testing Plate Tectonics

  1. Describe paleomagnetism.
  2. What is the difference between normal polarity and reverse polarity?
  3. What is the strongest evidence of seafloor spreading?
  4. Scientists found a close link between deep-focus ______and ocean ______. Also, the absence of deep-focus earthquakes along the ______system was shown to be consistent with the new theory.
  5. What did the Deep Sea Drilling Project from 1968 to 1983 find?
  6. The data on the ______of seafloor ______confirmed what the seafloor-spreading hypothesis predicted. The ______oceanic crust is at the ______and the ______oceanic crust is at the ______margins.
  7. What is a hot spot?
  8. What does hot spot evidence show?

Section 5 – Mechanisms of Plate Motion

  1. Scientists generally ______that ______occurring in the mantle is the basic ______force for ______movement.
  2. What is convective flow?
  3. If the movements of the plates and mantle are driven by the unequal distribution of Earth’s heat, what is generating the heat?
  4. What does slab-pull mean in plate motion?
  5. What does ridge-push cause?
  6. What are mantle plumes?
  7. Briefly describe the whole-mantle convection model.
  8. The unequal distribution of heat within Earth causes the ______convection in the ______that ultimately drives plate motion.