Unit 1 Study guide: Earth Structure & Plate Tectonics The drawing below shows a cross section of Earth’s surface and its underlying mantle. At this particular location of the surface, the dense oceanic plate is being forced beneath the less dense continental crust. The dense oceanic plate experiences higher temperatures (and pressures) as it is forced deeper into the mantle. This interaction between the oceanic plate and continental plate causes molten material to move upward through the continental plate until it breaks the surface in the form of volcanoes. Use this diagram to answer these questions. Unit 1 Study guide: Earth Structure & Plate Tectonics Name:__________________________ Date: _________Block:_________   4. Just beneath point T on the drawing is a tropical island. What will eventually happen to the island as the oceanic plate moves?   WHY?    5. Just beneath point I on the drawing is an ancient impact crater in the ocean floor where a giant comet collided with Earth. What will happen to the ancient impact crater as the oceanic plate moves? WHY? 6. Imagine that an impact occurred on the continental plate millions and millions of years ago, leaving behind an impact crater near the right side of the base of the volcano. Why would there be little evidence of this impact crater found today? 7. Consider the rocky and crater-covered Moon. Its very old surface has remained virtually unchanged over the last few billion years. Do you think the Moon has an active, hot and molten interior or an inactive, cold and solid interior?  8. If a new planet were discovered, what evidence would you look for to determine whether or not it has an active, hot and molten interior? oceanic plate upward moving molten rock 1. In the drawing above, which way (right or left) are the oceanic and continental plates moving? Circle your answer choice for each plate type. oceanic – right or left continental – right or left   Which is hotter, the piece of mantle material at Position A or the piece of mantle material at Position D? The mantle material is hotter at Position _____ because . 3. What direction are the pieces of mantle material moving (up, down, left or right) at Positions A, B, C and D? Circle the direction for each position. Position A up down left right Position B up down left right Position C up down left right Position D up down left right

Why did you choose that location? Divergent boundaries are created where the crust is separating. This can occur on land or under the ocean. A divergent boundary in the center of an ocean is shown below with arrows showing the direction the crust is moving. 9. Where is the oldest crust found? Circle the letter below that represents your answer choice.   A B C Why did you choose that location? 10. If each plate is moving at a rate of 2 cm per year, roughly how long did it take for Rock C to reach its current location? Circle your answer choice. 0 years 2 years 4 years 8 years 11. What is the age of the rocks at location A? Circle your answer choice. 0 years 1.5 years 3 years 4.5 years 12. What is the age of the rocks at location B? Circle your answer choice. 13. What is the age of the rocks at location C? Circle your answer choice. 14. Why should your answers to Questions #11 and #14 match? Revise your answers if necessary. The Atlantic Ocean is a primary example of a seafloor spreading type of divergent boundary. Use the map of the ages of the seafloor in the Atlantic Ocean to answer the following questions. 17. Does the pattern of ages match your answer to Questions #10-14? Revise your answer if necessary.       18. Approximately how long ago did the Atlantic Ocean begin to form? 19. You are reading a proposal requesting money to search for evidence of a crater that caused a mass extinction on Earth 245 million years ago. The team is proposing to search a poorly explored area of the floor of the Atlantic Ocean between South America and northern Africa. Would you fund this project? Use the ages of the seafloor to support your answer. 15. A map of the Atlantic Ocean is shown to the right. Where are the oldest rocks in the Atlantic found? Circle one of the choices below. Location D Location E   Briefly explain your answer. 16. Two students are debating about the relative ages of the rocks in the Atlantic Ocean. Student 1: The oldest rocks are located at E because it is the farthest from a continent. The rocks would take a really long time to get to the middle of the ocean. Student 2: But this ocean has a divergent boundary in the center. This means that rocks at E are really young. D is farthest from the divergent boundary, so that’s where the oldest rocks are. With which student do you agree? Why?

26. Continental Margins – use your notes to complete the table below 22. Two students are discussing the features they labeled on the diagram.   Student 1: I labeled the ocean plate, the continental plate, volcanoes, and mountains. Student 2: I labeled those, plus the ocean trench and subduction. Student 1: I like that you labeled the trench, but I don’t think you can label subduction. Subduction is an action of something happening, and it’s not a feature. Student 2: But you can see it on the diagram where the ocean plate is being pushed under the continental plate, so I think you can label subduction as a feature. With which student do you agree? Why? 23. Could you go to a convergent plate boundary and watch subduction happening? yes no 24. If you can watch subduction happening, what would you see? 25. If you cannot watch subduction happening, what can you look for to indicate that subduction is happening? Subduction Features - Use the diagram above to answer questions 24-29. The cross section below shows a subduction zone at an ocean-continent convergent boundary. The ocean surface is indicated by a dashed line. 20. Draw arrows showing which way the plates are moving.   21. On the diagram, label every feature that geologists can see on the Earth’s surface related to plate tectonics. A feature is a thing you can see and not something that is happening. 26. Continental Margins – use your notes to complete the table below 27. Deep Ocean Basins – List the deep ocean basin features you would expect to find. active passive boundary type geologic features

Plates show movement over time Plates show movement over time. The cross sections below show subduction zones at an ocean-continent convergent plate boundary. 28. Consider Cross Section #2. Where was “L” in the past? J K L M N same place 29. Consider Cross Section #2. Where will “J” be in the future? J K L M N same place   Two students are discussing how the square on the continental plate will move over time relative to the volcano. Student 1: I think that the square will stay in the same place relative to the volcano because the ocean plate is the plate that is subducting and is destroyed. The continental plate isn’t destroyed, so the square doesn’t move. Student 2: But it’s a convergent boundary, and the plates are moving together. Because I can draw arrows showing the plates moving together, that means that the square is moving towards the ocean plate and away from the volcano. 30. With which student do you agree? Why? 31. Consider Cross Section #2. Is it possible for “L” and “K” to be next to each other in 50 million years? yes no Explain your answer. Two students are discussing whether star and the square will be next to each other in the future. Student 1: I think they will still be next to each other because it’s a convergent boundary, and the ocean plate is subducting. Everything is moving down, so they’ll move down together. Student 2: They won’t be next to each other because the star is on the ocean plate, which is subducting. But the continental plate is not, so the square stays in the same place. 32. Consider Cross Section #2. With which student do you agree?

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