Study Guide for Sections 9.4

Name: _____________________________________________ Date: ________
Study Guide for Sections 9.4 and 9.5
Pages 265-270
Section 9.4: Three Pieces of Evidence for Plate Tectonics
I. Paleomagnetism- Paleo in Greek means “ancient”
a. Earth’s magnetic field is much like that produced by a
b. How do rocks become magnetized?
c. Define normal polarity and reverse polarity:
d. What is the strongest evidence of seafloor spreading?
Name: _____________________________________________ Date: ________
e. Observe figure 17 and answer the following questions:
Why are the magnetized strips about equal width on either side of
the ridge?
How do you think the width of the strip relates to the seafloor
spreading rate?
II. Earthquake Patterns
a. Observe figure 18 and answer the following questions:
The most shallow-focus earthquakes occur next to the
The intermediate and deep focus earthquakes occur toward the
From the map, identify the direction in which the sinking slab of
oceanic crust is moving.
Locate Korea on the map. Why do you think Korea has relatively
few earthquakes compared to Japan?
Name: _____________________________________________ Date: ________
III. Ocean Drilling
a. When the oldest sediment from each drill site was plotted against its
distance from the ridge; it was revealed that the age of the sediment
____________________ with increasing distance from the ridge.
b. The ___________________oceanic crust is at the ridge crest and the
____________________ oceanic crust is at the continental margins.
c. The data also reinforced the idea that that the ocean basins are
geologically young. No sediment older than __________________ was
found. By comparison, some continental crust has been dated at
IV. Hot Spots
a. Define:
b. Observe figure 19 and answer the following questions:
 What is the direction of plate motion for the Pacific plate?
What island is the oldest in the Hawaiian chain?
Are all the volcanic islands in figure 19 still active today? Why or
Why not?
Where will a new Hawaiian island be located?
Section 9.5 Causes of Plate Motions
a. What do scientists agree is the basic driving force for plate movement?
Name: _____________________________________________ Date: ________
b. Explain what happens during this process.
c. Explain the slab-pull mechanism.
d. Explain the ridge-push mechanism.
e. What is a mantle plume?
f. How do mantle plumes show themselves on Earth’s surface? Give an