Download Section: Continental Drift

Pangea and Continental Drift
WEGENER’S HYPOTHESIS
______1 . The German scientist Alfred Wegener proposed a hypothesis now called
a. paleomagnetism.
c. floating continents.
b. continental drift.
d. sea-floor spreading.
______ 2. Wegener hypothesized that the continents formed part of a single land mass, or
a. mid-ocean ridge.
c. supercontinent.
b. monocontinent.
d. world land.
______ 3. Wegener speculated that over millions of years these small continents
a. moved closer together.
c. drifted to the southern hemisphere.
b. did not move.
d. drifted to their present locations
4. Why was Wegener interested in finding fossils of the same plants and animals on two different
continents?
5. Where were the fossils from the extinct land reptile called Mesosaurus found?
6. Why did Wegener believe that the fossils found in South America and western Africa proved that
South America and Africa had once been joined?
7. How did the ages and types of rocks found in some coastal areas of Africa and South America
support Wegener’s hypothesis?
8. How did the locations of mountain chains support Wegener’s hypothesis?
9. Give an example of a mountain chain that seems to continue from one continent to other continents
across the ocean.
10. What do layers of debris from ancient glaciers in southern Africa and South America indicate to
geologists?
11. What evidence shows that tropical or subtropical swamps used to cover areas that now have
colder climates?
12. How did Wegener account for differences in climate between the past and today?
MID-OCEAN RIDGES
______ 13. Undersea mountain ranges with steep, narrow valleys in the center are called
a. black smokers.
c. mid-ocean ridges.
b. the Mid-Atlantic Ridge.
d. sea floor ridges.
______ 14. Compared to rocks farther from a ridge, rocks closer to a ridge are
a. older.
b. younger.
______ 15. The oldest ocean rocks are
a. 3.8 billion years old.
b. 175 million years old.
c. more than 175 million years old.
d. older than rocks on land.
SEA-FLOOR SPREADING
16. Describe the process of sea-floor spreading.
PALEOMAGNETISM
17. In what way is Earth like a giant magnet?
18. Explain how solidified magma comes to be magnetic.
19. Why do scientists think that Earth’s magnetic field has not always pointed north?
20. On a map of the ocean floor, what do the magnetic patterns show?
21. What did scientists think happened to cause the magnetic patterns they found?
______22. Where were the youngest rocks on the sea floor?
a. center
b. further away
______23. Where were the older rocks on the sea floor?
a. center
b. further away
______24. Where does new rock form on the sea floor?
25. What do sea-floor rock patterns indicate about how rock forms?
WEGENER REDEEMED
______ 26. Scientists have found evidence of reversal patterns in
a. rocks only on the ocean floor.
b. rocks only on land.
c. rocks on the ocean floor and on land.
d. rocks from the moon.
______ 27. The mechanism that verifies Wegener’s hypothesis of continental drift is
a. geomagnetic reversal.
c. sea-floor contracting.
b. magnetic symmetry.
d. sea-floor spreading.
CAUSES OF PLATE MOTION (page 253)
______ 28. The movement of heated material due to differences in density
is called
a. convection.
c. radioactivity.
b. a convection cell.
d. plate motion.
______ 29. The cycle in which the cooler, denser water sinks and the warmer
water rises to the surface to create a cycle is called
a. convection.
c. a convection cell.
b. plate tectonics.
d. boiling water.
______ 30. Earth’s mantle is heated by
a. tectonic plates.
b. core energy and radioactivity.
c. boiling water.
d. cool, dense mantle material.
______ 31. What causes tectonic plate movement?
a. Hot material in the mantle sinks.
b. Lack of a convection cell causes plates to
rise.
c. The mantle drags overlying tectonic plates
along.
d. Divergent boundaries come together.
32. What happens as a result of ridge push?
33. What happens to magma in places where plates pull away from each other at mid-ocean ridges?
34. What three forces work together to cause plate motions?