Oceanography 10 Name:___________________________________
Plate Tectonics Study Guide (Topic 11A)
Plates, Lithosphere, Crust, and the Mantle:
Read Unit 11A-1 (Plate Tectonics, The Lithosphere and the Crust) and Unit 11A-3 (Why do the plates move?, Plate Speed and Measuring Plate Motion, and A single plate often contains both continental lithosphere and oceanic lithosphere)
1. Describe what is meant by a “plate” in the theory of plate tectonics.
2. How is the lithosphere (crust) different from the mantle? Which one is thin and which one takes up much of the inside of the Earth? Which is warmer and which is cooler? Which one can flow (“ooze”) and which one is solid?
Circle the picture which best describes the layers of the Earth, and write “lithosphere (crust)”
and “mantle” next to the appropriate arrows indicating the layers.
Core Core Core
3. Describe and compare continental and oceanic lithosphere (crust).
What kind of rock is continental lithosphere (crust) made of? ________________________
What kind of rock is oceanic lithosphere (crust) made of? ________________________
How is their appearance different?
How could you tell them apart? __________________________________________
Which has a higher density, granite or basalt? ________________________
4. The Relative Density of the Lithosphere (Crust) and the Mantle
Which has a higher density, granite or the mantle? ________________________
Which has a higher density, basalt or the mantle? ________________________
5. “A single plate CAN be made of large amounts of BOTH continental and oceanic lithosphere.”
● True: The continental lithosphere is on top the oceanic lithosphere.
● True: The oceanic lithosphere is on top of the continental lithosphere.
● True: The continental lithosphere and oceanic lithosphere are attached side-by-side.
● False: A plate is only made of ONE kind lithosphere, NOT BOTH.
6. About how fast do plates of the Earth’s crust typically move?
Observations which support the theory of plate tectonics:
Read Unit 11A-1
7. Which of the following observations are consistent with and have been used to support the theory of plate tectonics? (Circle all that apply.)
● Fossils of identical plants & land animals are found on 2 or more continents separated by oceans.
● Fossils of tropical animals and plants are only found in the tropics.
● The layer of ocean sediments covering the ocean floor is thicker on the abyssal plains than on the mid-ocean ridge.
● A layer of red clay is found on top of a layer of calcareous ooze on the abyssal plains.
● Most trenches are found in the middle of the ocean, far from land (continents and islands).
● The oceanic lithosphere near the mid-ocean ridge is younger than the lithosphere farther from the ridge.
● The oceanic lithosphere far from a trench is older than the lithosphere closer to the trench.
● Some kinds of rocks and mineral deposits (e.g., coal, diamonds) are found near the coast and on opposite sides of the Atlantic ocean.
Which of the following observations about earthquakes and volcanoes have been used to support the theory of plate tectonics? (Mark all that apply.)
Earthquakes typically occur at or near: Most volcanoes are found at or near:
● the abyssal plains ● the abyssal plains ● continental shelves ● continental shelves ● continental slopes ● continental slopes ● the mid-ocean ridge ● the mid-ocean ridge
● trenches ● trenches
● The locations of earthquakes do not ● The locations of volcanoes do not support the theory of plate tectonics. support the theory of plate tectonics.
8. “The magnetic north pole is at the same spot on Earth’s surface True / False as the geographic or “true” north pole.”
“The magnetic north pole of the Earth has never moved. True / False It has always been in the same place.”
Plate Motion and How It Creates and Destroys:
Read Unit 11A-1 (Plate Tectonics, The Lithosphere and the Crust, and The Basics of the Theory of Plate Tectonics), and Unit 11A-2 (Plate Boundaries, Divergent Boundaries, Oceanic Lithosphere meets Continental Lithosphere, Oceanic Lithosphere meets Oceanic Lithosphere), and Unit 11A-3 (Why do plates move? and Volcanoes near Trenches)
9. What causes the plates to move? In other words, what pushes the plates in the directions shown?
10. Describe the motion of the plates. What feature of the ocean floor do they move away from? What features of the ocean floor do they move towards?
11. How or why is new ocean floor created at the mid-ocean ridge? As part of your answer, explain how the motion of the plates causes lava to come up at the mid-ocean ridge.
12. Which plate dives down into the Earth when two plates collide, the higher-density plate or the lower- density plate? What feature of the ocean floor is created by this process?
13. How or why is a plate destroyed when it dives down deeper into the Earth?
Plate Density and Plate Motion
Read Unit 11A-1 (Plate Tectonics, The Lithosphere and the Crust, and The Basics of the Theory of Plate Tectonics), and Unit 11A-2 (Plate Boundaries, Divergent Boundaries, Oceanic Lithosphere meets Continental Lithosphere, Oceanic Lithosphere meets Oceanic Lithosphere), and Unit 11A-3 (Volcanoes near Trenches)
14. What is continental lithosphere made of, basalt or granite What is oceanic lithosphere made of basalt or granite?
15. Which has a higher density, basalt or granite?
16. Which has a higher density, basalt or the mantle?
17. Which has a higher density, granite or the mantle?
18. What feature of the ocean floor is created when two plates collide and one plate goes down underneath the other plate (subducts): abyssal plains, the continental shelf, then continental slope, the mid-ocean ridge, or a trench?
19. When the side of a plate made of continental lithosphere collides with the side of a plate made of oceanic lithosphere, which one dives down into the Earth (subducts)? Why?
20. As a plate made of oceanic lithosphere gets older, does it become more dense or less dense? Why?
21. When the side of a plate made of oceanic lithosphere collides with the side of another plate made of oceanic lithosphere, which one dives down into the Earth (subducts)? Why?
22. When the side of a plate made of continental lithosphere collides with the side of another plate made of continental lithosphere, why doesn’t either plate dive down into the Earth (subduct)?
23. When the side of a plate made of continental lithosphere collides with the side of another plate made of continental lithosphere, what do the plates do instead of going down? What feature of the land is created as a result of this motion: islands, mountains, the mid-ocean ridge, or a trench?
24. Why is the mid-ocean ridge much higher (less deep) than the abyssal plains on either side of it?
Subduction Zones: Trenches, Volcanoes, Mountain Chains, and Island Chains Read Unit 11A-1 (Plate Tectonics, The Lithosphere and the Crust, and The Basics of the Theory of Plate Tectonics), and Unit 11A-2 (Plate Boundaries, Divergent Boundaries, Oceanic Lithosphere meets Continental Lithosphere, Oceanic Lithosphere meets Oceanic Lithosphere), and Unit 11A-3 (Volcanoes near Trenches)
25. Where is oceanic lithosphere (crust) being destroyed on the ocean floor:
on abyssal plains, on continental shelves, on continental slopes, at the mid-ocean ridges, or at trenches? How or why is oceanic lithosphere destroyed at these locations?
26. Why do volcanoes grow next to trenches?
27. Where does the lava in subduction zones come up: beneath the plate which is diving down into the Earth, beneath the plate which is NOT diving down into the Earth, or in the trench?
28. Why are chains of islands found along the edges of trenches that are not next to continents?
29. Why are chains of mountains found along the coast of continents next to trenches?
30. True or false? “When the side of a plate made of continental lithosphere collides with the side of a plate made of oceanic lithosphere, the oceanic lithosphere goes down below the continental lithosphere and lifts it up, creating mountains.”
31. True or false? “When the side of a plate made of oceanic lithosphere collides with the side of another plate made of oceanic lithosphere, one plate goes down below the other one and lifts it up, creating islands.”
Plate Motion
Read Unit 11A-1 (Plate Tectonics, The Lithosphere and the Crust, and The Basics of the Theory of Plate Tectonics), and Unit 11A-2, and Unit 11A-3
(Why do plates move? and Volcanoes near Trenches) 32. Label the mid-ocean ridge, the trench, and
the mantle in the side-view picture on the right.
33. Sketch arrows showing the motion of magma of the mantle into the side-view picture on the right.
Use the shape of the ocean floor and the rest of surface of the Earth to deduce how the magma of the mantle is moving.
34. Do plates move towards or away from the mid-ocean ridge?
35. Do plates move towards, away from, or parallel to transform faults?
36. In the picture on the right, the solid lines represent the mid-ocean ridge, and the dotted lines represent transform faults.
Sketch arrows either side of the ridge that show the motion of the plates (the direction the ocean floor is moving in).
Add V’s at locations where volcanic activity occurs.
Add E’s at locations where earthquakes occur.
N
S E W
P Map #1
N
S E W
P Map #2
37. On the maps on the right:
(a) Highlight the mid-ocean ridge in red, the transform faults in blue, and the trenches in green. (See the legend on upper right part of this page. It will help you identify them.) (b) With a grey pencil, highlight the edges of the plate that contains the letter “P.”
(c) Put an arrow (or arrows) on plate P showing the direction that the plate is probably moving in.
(d) Put small letter “E” in places where you think that earthquakes will be common in the map.
(e) Put small letter “V” in places where you think that volcanoes will be found on the map.
Hot Spots and Examples of Locations with Each Kind of Plate Motion
Read Unit 11A-1 (Plate Tectonics, The Lithosphere and the Crust, and The Basics of the Theory of Plate
Tectonics), and Unit 11A-2, and Unit 11A-3 (Volcanoes near Trenches, Hotspots and Volcanic Islands, Hotspot Island-Seamount Chains, Hotspot Island-Seamount Chains as Evidence of Sea-Floor Spreading, Hotspot Locations, The Causes of Hotspots, and Island-Seamount Chains are also found next to Trenches)
38. Why is there a volcano at a “hot spot”? (Circle all that apply.)
● A blob of hot magma that rose up from deep inside the earth melts through the lithosphere.
● Plates are moving apart at the hotspot, and lava from below it coming up into the gap.
● Two plates are colliding at the hot spot; the plate that is made of oceanic lithosphere is diving into the Earth and melting into lava.
● Two plates are colliding at the hot spot; the plate that is made of older lithosphere is diving into the Earth and melting into lava.
39. How does an island chain form near a hot spot? Explain.
40. Give a specific example of a place in the world where each of the following events is occurring:
(Be as specific as you can. Listing the name of a continent or country may not be enough.) new oceanic lithosphere (crust) is being created
oceanic lithosphere (crust) is colliding with continental lithosphere (crust) 2 pieces of oceanic lithosphere (crust) are
colliding with one another
2 pieces of continental lithosphere (crust) are colliding with one another
continental lithosphere (crust) has just split apart (or is beginning to) and a new “ocean”
is beginning to form in-between a hotspot
Plate Tectonics Practice:
Summary of How the Motion of Plates Creates Volcanoes, Mountains, and Island Chains
41. Describe the three different ways that volcanoes form according to the theory of plate tectonics.
Near the Mid-Ocean Ridge: Magma rises up from below to fill in the _____________ created when the plates move ________________________________ the mid-ocean ridge.
Near Trenches: The diving plate ___________ in the hot mantle, producing some low-density magma which rises up and melts its way through the plate above it.
Hot Spots: At some special places, magma rises up from deep in the mantle and melts through the lithosphere above.
42. Describe the two different ways that mountain chains form according to the theory of plate tectonics.
Volcanic Mountains, Close to Coast next to a Trench: The diving plate ___________ in the hot mantle, producing some low-density magma which rises up and melts its way through the plate above it.
Non-Volcanic Mountains, Inland (Away from the Coast): Two plates made of ______________ collide.
Neither can sink down into the mantle, because their density is much ___________________ than the density of the ________________, so rock rises upwards to make room for the rock that is being pushed together.
43. Describe the two different ways that island chains form according to the theory of plate tectonics.
Islands are ALL next to a Trench and ALL Islands are potentially Volcanic: The diving plate ___________
in the hot mantle, producing some low-density magma which rises up and melts its way through the plate above it. Lava comes up all along the edge of the trench, creating many volcanic islands.
Islands are NOT near a trench and only ONE Island is Volcanic: At some special places, magma rises up from deep in the mantle and melts through the lithosphere above it. A volcanic island grows above this spot, but is carried away from the spot because the plate it has grown on ____________. Another island begins to grow, and the process repeats.
Plate Tectonics Practice:
Plate Boundaries: All 3 kinds of plate boundaries summarized in one picture
Mark the locations of the mid-ocean ridge, transform faults, and the trench in the picture below.
Put the letter “E” in locations where earthquakes should typically occur, and put the letter “V” in locations where volcanic activity is likely.
Mantle
Lithosphere
Trench Mid-Ocean Ridge Transform Fault
Plate Tectonics Practice Maps
You can practice identifying the directions of plates and the locations of earthquakes and volcanoes using the maps below. Use the same legend as the “Plate Motion” portion of the study guide to identify the mid- ocean ridge, trenches, transform faults, and land in the maps below.
Plate A
Plate B
Plate C
Plate D
