ENV 151 Study Guide - Quiz Guide: Divergent Boundary, Continental Drift, Continental Crust

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13 Dec 2018
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Chapter 7
1. What group of geologists were the least receptive to the continental drift hypothesis?
Explain.
North American geologists were the least receptive because most of the evidence was
from Africa, South America, and Australia; these continents were unfamiliar to these
geologists.
2. What was the first line of evidence that led early investigators to suspect that the
continents were once connected?
Similarity of continental coastlines and jigsaw-like fit of the continents.
3. Explain why the discovery of the fossil remains of Mesosaurus in both South America and
Africa, but nowhere else, supports the continental drift hypothesis.
Mesosaurus was a freshwater reptile and could not have migrated across the ocean. In
addition, there is no evidence of any bridge or other connector between these two
continents.
4. Early in the twentieth century, what was the prevailing view of how land animals
migrated across vast expanses of open ocean?
Lower sea level and land bridges, rafting, and island stepping stones.
5. How did Wegener account for the existence of glaciers in the southern landmasses at a
time when areas in North America, Europe, and Asia supported lush tropical swamps?
Pangaea; southern continents were one landmass situated about the South Pole.
6. What major ocean floor feature did oceanographers discover after World War II?
Mid ocean ridge.
7. Compare and contrast the lithosphere and the asthenosphere.
The lithosphere is the hard outer portion of the Earth’s crust. The asthenosphere lies
beneath and is more ductile, allowing the lithospheric plates to “float” and be mobile.
8. List the seven largest lithospheric plates.
North American, South American, Pacific, African, Eurasian, Australian-Indian, and
Antarctic.
9. List the three types of plate boundaries and describe the relative motion at each of them.
Divergent plates move apart.
Convergent plates move towards each other.
Transform plates slide laterally past each other.
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