Plate boundaries in oceans part 1: features the cross section below shows the tectonic plates beneath an ocean and a nearby continent. the ocean surface is indicated by a dashed line. 1. draw arrows to show the directions the plates are moving near locations a and b. 2. two students are discussing the directions the plates are moving. student 1: 1 drew the arrows moving apart at location a because mogma is pushing the plates up as it rises to fill in the gap as the plates move apart. student 2: i drew the arrows moving together at location a because as the plates are moving toward each other, they get pushed up. with which student do you agree? why? 3. what seafloor feature is found of location a? 4. what seafloor feature is found of location b 5. what type of plate boundary is at location a? ridge trench abyssal plain island ridge trench obyssal plain island divergent convergent transform 6. what type of plate boundary is of location b divergent convergent transform 7. check that your answers for questions 5 and 6 match the arrows you drew at locations a and b in question 1. b. if you find a plate boundary in the middle of an ocean away from the edge, what type of plate boundary is it most likely to be? divergent convergent with subduction convergent without subduction 9. if you find a plate boundary along the edge of an ocean next to a continent, what type of plate boundary is it most likely to be? divergent convergent with subduction convergent without subduction © w. h. freeman and company lecture tutorials for introductory geoscience 32. plate boundaries in oceans below is a cross section of the ocean floor and nearby land showing the surface features. the ocean surface is indicated by a dashed line. 10. label the ocean ridge. 11. label the ocean trench. 12. label the mountains/volcanoes on land. 13. label the divergent boundary. 14. label the convergent boundary. 15. draw what the plates are doing beneath the surface to produce the surface features. w. h. freeman and company lecture tutorials for introductory geoscience 33. the age of the crust the cross section below shows the oceanic lithosphere (thinner, more dense) and continental lithosphere (thicker, less dense). the ocean surface is indicated by a dashed line. 1. label the divergent plate boundary and the convergent plate boundary 2. what type of lithosphere is created new at the divergent plate boundary oceanic lithosphere continental lithosphere 3. what happens to the old ocean lithosphere at the convergent plate boundary? it is pushed underneath the surface. it may change but stays at the surface. 4. what happens to the old continental lithosphere at the convergent plate boundary it is pushed underneath the surface. it may change but stays at the surface. 5. based on what happens to the old ocean lithosphere, is there any very, very old ocean lithosphere remaining on earth yes no 6. based on what happens to the old continental lithosphere, is there any very, very old continental lithosphere remaining on earth? yes no 7. label on the diagram where the oldest rock is at the surface. 8. which statement correctly describes the relative age of continental and oceanic lithosphere? continental rock is generally much older than oceanic rock. oceanic rock is generally much older than continental rock. 9. the oldest continental rock is approximately 4,000 million (4 billion) years old, while the oldest ocean rock is approximately 180 million years old. what happened to the ocean lithosphere that made up the ocean seafloor 4,000 million (4 billion years ago? © w. h. freeman and company lecture tutorials for introductory geoscience 35. the age of the crust 10. two students are discussing why rocks are older on continents. student 1: continental lithosphere is much farther from divergent plate boundar les than is oceanic lithosphere. the farther you move away from a divergent plate boundary, the older the rock gets student 2: that only applies to the one of the ocean rock. old ocean lithosphere is subducted and destroyed, but continental lithosphere is not destroyed by sub- duction, which is why old continental rock is still around. with which student do you agree? why? you are reading two proposals requesting money to search for the oldest rocks on earth proposal 1: search unexplored ocean floor beneath the ice caps in the arctic. proposal 2: search the middle of the australian continent. 11. which proposal would you fund? support your answer by explaining what happens to oceanic and continental lithosphere at tectonic plate boundaries. 12. the gray lines in the map below are divergent plate boundaries. at which location on the map is the crust older? explain your answer. a: atlantic ocean b: africa w. h. freeman and company lecture tutorials for introductory geoscience 36.