Earth & Space Science - Chapter 8 Test Review Guide How do the rocks of the crust and lithosphere compare? Rocks in the crust are less dense and made mainly of granite. The rocks in the lithosphere are more dense and made mainly of basalt Of what are the Earth’s moving plates composed? Lithosphere 3. Define: a. Lithosphere: The crust and upper mantle b. Asthenosphere: The layer within the mantle which is made of partially melted rock. Convection currents in this layer move the lithospheric plates. How have the Earth’s magnetic poles changed over geologic time? They have reversed. Magnetic North has pointed geographic south in the past.

Where are volcano and earthquake belts most often found? At plate boundaries. How were the Appalachian Mountains formed? They were formed from the collision of North America, North Africa & part of Europe. These continents eventually split giving rise to the Atlantic Ocean. What happens when a continental plate converges with an ocean plate? The ocean plate subducts beneath the continental plate. Where are cratons located? Within the present continents. How are the fossils in a terrane related to those in neighboring rock formations? The fossils differ from neighboring rock formations.

10. Approximately how many plates make up the Earth’s surface? About 12 (7 major and 18 minor) 11. What causes the lithospheric plates to move? Convection currents in the asthenosphere. 12. What direction do convection currents move that are associated with converging plates? With diverging plates? Converging – sinking currents Diverging – rising currents 13. List evidence for continental drift. Volcanoes & earthquakes; magnetism; sea-floor spreading; rock & fossil similarities on different continents. 14. Where would you find the highest elevations of sea floor? At a mid-ocean ridge or where plates are diverging. 15. Where would you find the hottest rocks in the lithospheric plates? Closer to the middle of a spreading center or near the rift zone.

16. At what type of boundary would you find a mid-ocean ridge? Diverging 17. At what type of boundary is the San Andreas Fault located? Transform or sliding 18. Where would you find the greatest stress in a sliding boundary? Along a fault line where there is no movement. 19. In what direction are SW California and the Pacific Plate moving? Northwest 20. What are deep-sea trenches? Areas where the material that is added to the lithosphere from the mid-ocean ridges is returned to the asthenosphere.

21. Where do deep-focus earthquakes originate? Below the Earth’s outer crust. 22. Where is the oldest part of the North American continent located? The Canadian Shield is located in Eastern Canada. 23. What is a craton? How does the age of rocks change as you move away from a craton? An ancient continental core. Rocks get younger as you move away from a craton (This is the opposite of age change as you move from the center of a mid-ocean ridge. Don’t get confused!) 24. How do continents grow? From deep-sea sediments, volcanic activity, river sediments and terranes. 25. What is a terrane? A block of lithosphere that collides with the continent (collision boundary)

26. How were the Himalayan Mountains formed? They formed from the collision between India and China. 27. List and describe the three major types of plate boundaries. Include geologic features which result from each. 1) Diverging Plates move apart; sea-floor spreading Trench, mid-ocean ridge, rift valleys, earthquakes & volcanoes 2) Converging Plates move together; subduction or collision Trenches, volcanic mountains, volcanic islands, mountains, earthquakes Transform/Sliding Plates slide past each other Earthquakes

List and describe the major subtypes of converging boundaries. A. Ocean-Ocean Subduction Once ocean plate plunges beneath the other Trench forms along boundary Volcanic Island Chain may form on overriding plate Earthquake activity Ocean-Continental Subduction Ocean plated plunges beneath continental plate Volcanic mountains form on overriding continental plate Collision Two continental plates collide High continental mountain chains form