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CHAPTER 1 An Introduction to Geology
1. Geology is the study of Earth. It is divided into two broad areas: physical geology is the study of
the composition of Earth materials as well as the processes that operate within Earth and upon its
surface; historical geology examines the origin and evolution of Earth, its continents, oceans,
atmosphere, and life.
2. Explain both the difference between physical and historical geology and how they are related.
3. Which of the following is not a subdivision of geology?
a. paleontology; b. astronomy; c. mineralogy; d. petrology; e. stratigraphy
4. Geology is part of the human experience. We can find examples of it in the arts, music, and literature.
A basic understanding of geology is also important for dealing with the many environmental problems
and issues facing society.
5. Why is it important for people to have a basic understanding of geology?
6. Describe some of the ways in which geology affects our everyday lives
7. Krakatau is in:
a. Italy; b. the United States; c. Indonesia; d. Japan; e. Australia.
8. The eruption of Krakatau:
a. killed thousands of people; b. created giant sea waves; c. produced spectacular sunsets around the
world; d. caused a global cooling of about 0.5ºC; e. all of these.
9. Geologists engage in a variety of occupations, the main ones being exploration for mineral and energy
resources. They are also becoming increasingly involved in environmental issues and making short- and
long-range predictions of the potential dangers from such natural disasters as volcanic eruptions and
earthquakes.
10. Describe two industries that employ geologists, and briefly discuss what geologists do in
each industry.
11. Earth is differentiated into layers. The outermost layer, or crust, is divided into continental and
oceanic portions. Below the crust is the upper mantle. The crust and upper mantle comprise the
lithosphere, which is broken into a series of plates. The lithosphere moves over the asthenosphere, a
zone that behaves plastically. Below the asthenosphere is the solid lower mantle. Earth's core,
which is beneath the lower mantle, is divided into an outer liquid portion and an inner solid portion.
12. Name the major layers of Earth, and describe their general composition.
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13. Into how many concentric compositional layers is Earth divided?
a. 1; b. 2; c. 3; d. 4; e. 5
14. Earth's core is inferred to be:
a. hollow; b. composed of rock with a high silica content; c. completely molten;
d. composed mostly of iron and nickel; e. completely solid.
15. The asthenosphere:
a. lies beneath the lithosphere; b. is composed primarily of peridotite; c. behaves plastically and flows
slowly; d. is the zone over which plates move; e. all of these.
16. The layer between the core and the crust is the:
a. mantle; b. lithosphere; c. sima; d. sial; e. innersphere.
17. The scientific method is an orderly, logical approach that involves gathering and analyzing facts about
a particular phenomenon, formulating hypotheses to explain the phenomenon, testing the hypotheses, and
finally proposing a theory. A theory is an explanation for some natural phenomenon that has a large
body of supporting evidence and can be tested.
18. Describe the scientific method, and explain how it may lead to a scientific theory.
19. Define scientific theory.
20. Which of the following statements about a scientific theory is not true?
a. it is an explanation for some natural phenomenon;
b. it has a large body of supporting evidence;
c. it is a conjecture or guess;
d. it is testable; e. none of these.
21. The man who proposed the hypothesis of continental drift was:
a. Hutton; b. Wegener; c. Hess; d. Lyell; e. Lovelock.
22. Briefly describe the Gaia hypothesis.
23. Plate tectonic theory provides a unifying explanation for many geological features and events. Plates
can move away from each other, toward each other, or slide past each other. The interaction between
plates is responsible for volcanic eruptions, earthquakes, and the formation of mountain ranges and ocean
basins.
24. Briefly describe the plate tectonic theory, and explain why it is a unifying theory
of geology.
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25. What fundamental process is believed to be responsible for plate motion?
a. hot spot activity; b. subduction; c. spreading ridges; d. convection cells; e. density differences.
26. What are the three types of plate boundaries?
27. Mid-oceanic ridges are examples of what type of boundary?
a. divergent; b. convergent; c. transform; d. subduction; e. answers (b) and (d).
28. The San Andreas fault separating the Pacific plate from the North American
plate is an example of what type of boundary?
a. divergent; b. convergent; c. transform; d. subduction; e. answers (b) and (d).
29. A plate is composed of the:
a. core and lower mantle; b. lower mantle and asthenosphere; c. asthenosphere and upper mantle;
d. upper mantle and crust; e. continental and oceanic crust.
30. Igneous, sedimentary, and metamorphic rocks are the three major groups of rocks. Igneous rocks
result from the crystallization of magma. Sedimentary rocks are formed by the consolidation of rock
fragments, precipitation of mineral matter from solution, or compaction of plant or animal remains.
Metamorphic rocks are produced when preexisting rocks are changed in response to elevated
temperature, pressure, or fluid activity, generally beneath Earth's surface.
31. What are the three major groups of rocks?
32. Which of the following is not a major rock group?
a. volcanic; b. igneous; c. metamorphic; d. sedimentary; e. none of these.
33. Which rock group forms from the cooling of a magma?
a. igneous; b. metamorphic; c. sedimentary; d. all of these; e. none of these.
34. The rock cycle illustrates the interrelationships between the internal and external processes of
Earth and among the three major rock groups.
35. Describe the rock cycle, and explain how it may be related to plate tectonics.
36. The rock cycle implies that:
a. metamorphic rocks are derived from magma;
b. any rock type can be derived from any other rock type;
c. igneous rocks only form beneath Earth's surface;
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d. sedimentary rocks only form from the weathering of igneous rocks;
e. all of these.
37. Time sets geology apart from the other sciences, except astronomy. The geologic time scale is the
calendar geologists use to date past events.
38. The principle of uniformitarianism is basic to the interpretation of Earth history. This principle
holds that the laws of nature have been constant through time and that the same processes operating
today have operated in the past, albeit at different rates.
39. What is the principle of uniformitarianism? Does it allow for catastrophic events?
Explain.
40. The premise that present-day processes have operated throughout geologic time
is known as the principle of:
a. plate tectonics; b. sea-floor spreading; c. continental drift; d. Gaia; e. uniformitarianism.
41. Briefly discuss the importance of having a scientifically literate populace.
asthenosphere
atmosphere
biosphere
catastrophism
continental drift
convergent plate boundary
core
crust
divergent plate boundary
fossil
fossil succession
principle
geologic time scale
geology
historical geology
hydrosphere
hypothesis
igneous rock
lithosphere
magma
mantle
metamorphic rock
physical geology
plate
plate tectonic theory
principle of superposition
principle of uniformitarianism
relative dating
rock cycle
scientific method
sea-floor spreading
sediments
sedimentary rock
subduction zone
theory
transform fault plate boundary