Question 2.6

Why are there active volcanoes along the Pacific coast in Washington and Oregon but not along the east coast of the United States?

Question 2.7

What mistakes did Wegener make in formulating his theory of continental drift? Do you think the geologists of his era were justified in rejecting his theory?

Question 2.8

Would you characterize plate tectonics as a hypothesis, a theory, or a fact? Why?

Question 2.9

How do the differences between continental and oceanic crust affect the way lithospheric plates interact?

Question 2.10

In Figure 2.15, the isochrons are symmetrically distributed in the Atlantic Ocean, but not in the Pacific Ocean. For example, seafloor as much as 180 million years old (in darkest blue) is found in the western Pacific, but not in the eastern Pacific. Why?

Question 2.11

The theory of plate tectonics was not widely accepted until the banded patterns of magnetism on the ocean floor were discovered. In light of earlier observations—the jigsaw-puzzle fit of the continents, the occurrence of fossils of the same life-forms on both sides of the Atlantic, and the reconstruction of ancient climate conditions—why are these banded patterns of magnetism such a key piece of evidence?