GEOLOGIC TIME DIRECTED READING – EARTH SCIENCE - DUACSEK
CH 8 DIRECTED READING – Read p. 185 Uniformitarianism, 186 relative age, 187 superposition, 189
unconformity, 191- 3, 196 - 200
1. How old is Earth estimated to be?
2. What is the principle of uniformitarianism?
3. In what way is the principle of uniformitarianism important to the science of geology?
4. Layers of rock are called ___________.
5. The order of rock layers reveals
a. the type of rock in the layers.
b. the relative age of the layers.
c. the exact years in which each layer formed. d. periods of volcanic activity.
6. Relative age indicates
a. the true age of the rock layers.
b. that all rock was formed at the same time.
c. the amount of erosion in a rock layer.
d. that one rock layer is older than another layer.
7. Although various types of rock form layers, what type of rock is commonly used by scientists to determine the
relative age of rocks?
a. igneous rock
b. metamorphic rock
c. sedimentary rock
d. superheated rock
8. Layers of compressed and hardened sediments are called _____________.
9. The law of superposition helps scientists determine the
a. relative age of a layer of sedimentary rock.
b. true age of a layer of sedimentary rock.
c. composition of a layer of sedimentary rock.
d. rate at which a layer of sedimentary rock will erode.
10. What can scientists assume when sedimentary rock layers are not horizontal?
a. The rock has been tilted or deformed.
b. The rock is not actually sedimentary.
c. The rock has been eroded.
d. The law of superposition is wrong.
11. What causes sedimentary rock layers to be tilted or deformed?
a. erosion by water
b. lava flows from volcanoes
c. movements of Earth’s crust
d. the weight of new layers of sediment
12. When sedimentary rock is tilted or deformed, scientists know that crustal movements occurred
a. while lava was flowing.
b. before the rock was formed.
c. while the rock was forming.
d. after the rock was formed.
27.1 DIRECTED READING
13. When Earth formed, its high temperature was NOT due to
a. heat produced when planetesimals collided with one another.
b. heat generated when the increasing weight of its outer layers compressed its inner layers.
c. the conversion of moving radioactive particles into heat energy.
d. an irregular orbit that brought it closer to the sun.
14. Which of the following did NOT form as one of Earth’s layers when differentiation occurred?
a. core
b. mantle
c. atmosphere
d. crust
15. Which of the following elements is NOT present in large amounts in Earth’s three layers?
a. gold
b. iron
c. silica
d. magnesium
16. Earth’s surface continued to change as a result of
a. increasing radiation.
b. colliding planetesimals.
c. the heat in Earth’s interior.
d. hydrogen fusion.
17. The original atmosphere of Earth consisted of
a. oxygen and nitrogen.
b. hydrogen and helium.
c. nitrogen and helium.
d. hydrogen and oxygen.
18. Today, hydrogen and helium occur mainly in the
a. oceans.
b. middle atmosphere.
c. lower atmosphere.
d. upper atmosphere.
19. Earth’s early atmosphere formed when volcanic eruptions released gases in a process called
____________________________.
20. The rotating cloud of dust and gas from which our solar system is thought to have formed is called the
____________________________.
21. What is the molecule that contains three oxygen atoms and collects in Earth’s upper atmosphere called?
DUACSEK GEOLOGIC TIME 1
22. Some of Earth’s early organisms, such as cyanobacteria and early green plants, used ______________ during
photosynthesis.
23. Which byproduct of photosynthesis was released into the atmosphere?
24. When did the chemical composition of Earth’s atmosphere reach that of today?
25. What is the present chemical composition of Earth’s atmosphere?
26. How did Earth’s first oceans form?
27. Comet collisions may have contributed a significant amount of _______________to Earth’s surface.
28. The first ocean was probably made of ____________ water.
29. The concentration of certain _________________ in the oceans increased as rainwater dissolved rocks on
land and carried these dissolved solids into the oceans.
30. When ocean water evaporated, chemicals in the ocean combined to form ______________
31. Earth’s atmosphere and surface cooled because ocean water also dissolved much of the ______________ in
the atmosphere.
32 . For what geological information are fossils an important source?
a. learning whether rock is sedimentary, igneous, or metamorphic
b. finding the absolute and relative ages of rocks
c. seeing the erosion patterns on ancient rocks
d. learning whether rocks have intrusions or faults
33. What is one way scientists can tell if an area of land was once covered by an ocean?
34. What usually happens to dead plants or animals?
a. They become fossils.
c. They are eaten or decomposed by bacteria.
35. What does a cast show about an animal?
b. They just stay where they are.
d. Nothing happens to them.
36. A trace fossil is _________________________________________________________
37. Fossils that are found only in the rock layers of a particular geologic period are called _________________.
38. What is most important about the features of an index fossil?
a. Its features must be recognized as coming from other organisms that became fossils.
b. Its features must be equally clear in each of the different fossils found.
c. Its features must differ according to the location on Earth in which it is found.
d. Its features must clearly distinguish it from other fossils.
39. Rock layers in which index fossils have been found can be dated accurately because the organisms that formed
the index fossils lived
a. for a long span of geologic time.
b. for a short span of geologic time.
c. all over Earth.
d. in a small part of Earth.
CH 9 DIRECTED READING
40. The ordered arrangement of rock layers is called a(n) _____.
41. What two things distinguish a rock layer in a geologic column?
42. How do the fossils in the upper layers of a geologic column differ from those in the lower, older layers?
43. What three indicators do geologists use to divide the geologic time scale into smaller units?
44. A unit of geologic time is usually characterized by_______________ of a dominant life-form.
45. What species were common during the Cambrian Period?
46. During which period did the age of fishes begin?
47. What was the dominant life-form of the Jurassic Period?
48. What kinds of fossils are found in rocks from the Paleozoic Era?
49. The present geologic era is called the ____________________________.
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50. When did the present geologic era begin?
51 Climatic and geologic changes could affect an organism’s ability to ._____________.
52 . What is a nebula?
53. When did the Earth form?
54. The time interval that began with the formation of Earth is called _____________________.
55. About how much of Earth’s history occurred during Precambrian time?
56. Name three possible reasons why fossils are rare in Precambrian rocks.
57. When the Paleozoic Era began, Earth’s landmasses were
a. arranged much as they are today.
b. located in a single region of the world.
c. unstable due to tectonic activity.
d. scattered around the world.
58. brachiopod
a. a fossil that scientists use to date rocks
59. invertebrate
b. the most common Cambrian invertebrate
60. index fossil
c. a shelled animal common during the Cambrian Period
61. trilobite
d. an animal that does not have a backbone
62. In what period did the first land plants and land animals evolve?
63. Briefly describe the climate during the Carboniferous Period.
64. What animals survived the environmental changes at the end of the Permian Period?
65. What occurs during a mass extinction?
a. All species die off.
c. Organisms adapt to environmental change.
66. What is another name for the Mesozoic Era?
b. Large numbers of species die off.
d. Most life-forms survive.
67. What are two theories about the cause of the mass extinction at the end of the Cretaceous
Period?
68. What caused the uplifting of the Himalayas?
69. When did the largest known land mammals live?
DUACSEK GEOLOGIC TIME 3