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”
Define:
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
example.