Laboratory Manual for Introductory Geology 4e

More clues soon came from seismologists (geologists who study earthquakes).
Records showing the locations of earthquakes worldwide revealed a concentration
along linear belts (FIG. 2.6). Although this pattern was more complex than that for
volcanoes, particularly in the deep ocean and in continental interiors, the two patterns
demonstrated important similarities. Something unique was happening along
the volcanic chains and where earthquakes occurred, but geologists couldn’t agree
on what that was. In Exercise 2.3 you will follow the reasoning geologists used to
build the basic framework of plate tectonics theory.
FIGURE 2.6 Worldwide distribution of earthquakes, 1960–1980.
Atlantic
Ocean
Indian
Ocean
Pacific
Ocean
Shallow earthquakes
Intermediate earthquakes
Deep earthquakes
EXERCISE 2.3
Putting the Early Evidence Together
Name:
Course:
Section:
Date:
Examine the patterns shown in Figures 2.5 and 2.6 and answer the following questions to understand the initial reasoning
underlying plate tectonics theory.
(a) Where are the volcanic and earthquake patterns most similar?
(b) In what parts of the world are there abundant earthquakes but not (apparently) active volcanoes?
(continued )
32 CHAPTER 2 THE WAY THE EARTH WORKS: EXAMINING PLATE TECTONICS