AnswersDCSS Earth Systems CR 24-25Unit Test

Unit Test — Unit test Answers

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1
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After two half-lives, how much of the original material has decayed?

A
25 percent
B
50 percent
C
75 percent
D
100 percent
2
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For which object would a geologist use carbon-14 dating to determine age?

A
The bones of animals
B
Rocks older than 50,000 years old
C
Types of Sedimentary rocks
D
Parts of Volcanic rock
3

Which is one piece of information that fossils in samples from Earth’s crust reveal about Earth’s history?

A
changes in climate
B
number of species at a specific time
C
composition of Earth’s core
D
age of organisms when they died
4

The image shows flat sedimentary rock layers in the foreground and angled sedimentary rock layers in the background.

Question illustration
A
They cracked at an angle.
B
They were deposited at an angle.
C
They were deposited vertically and then shifted by a geologic event.
D
They were deposited horizontally and then shifted by a geologic event.
5

Which best explains a primary reason for the inability of life to exist in Earth’s early atmosphere?

A
There was insufficient energy from material collisions to change their density.
B
High temperatures during Precambrian time caused surface water evaporation.
C
Volcanic eruptions and comet collisions added different gases to the atmosphere.
D
Available oxygen was used to help create an ozone layer within Earth’s atmosphere.
6

How might an entire insect be preserved?

A
Soft and hard tissues turn the insect into rock.
B
Tree sap flows over the insect and hardens.
C
Sediment accumulates over the insect and hardens.
D
Carbon from the decaying insect leaves a print on a rock.
7

Which best describes eras and periods?

A
Eras have a smaller time span than periods.
B
Eras and periods are independent of each other.
C
Eras and periods both appear at the start of the Cambrian period.
D
Eras were more recently established on the time scale than periods.
8

The image shows cross-cutting relationships. B, W, E, and K represent rock layers, and Q represents a fault.

Question illustration
A
Layer K is the oldest.
B
Layer W is the youngest.
C
Fault Q occurred before layer K was deposited.
D
Layers B, W, and E were deposited after fault Q occurred.
9

Study the diagram of the geologic time scale.Which method is most likely used to identify what happened before the start of the Paleozoic era?

Question illustration
A
Scientists study fossils from the Jurassic period.
B
Scientists observe index fossil records of the Mesozoic era.
C
Scientists examine fossil evidence during the Precambrian time.
D
Scientists explore the emergence of mammals and humans in the Cenozoic era.
10

Which feature causes a gap in the geologic record?

A
extrusion
B
fault
C
intrusion
D
erosion
11

Which phrase describes the relative age of a rock?

A
uses the law of superposition to determine which rock is older or younger
B
can determine the age based on location of a rock within the same layer
C
requires only one rock to determine the age
D
can provide the exact age of a rock
12

Which is the first step in the process during the formation of molded fossils?

A
Sediment hardens into rock.
B
Sediment is eroded from rock.
C
Organisms are buried under sediment.
D
Organisms' shapes are preserved in rock.
13

Which correctly lists the three isotopes that geologists measure to determine the age of an organism’s remains?

A
argon, nitrogen, and carbon-12
B
carbon-14, nitrogen, and carbon-12
C
nitrogen, potassium, and carbon-14
D
carbon-12, potassium, and argon
14

Which information can be determined using half-life?

A
age of material
B
type of particle released
C
percentage of rock that has aged
D
number of radioactive particles left
15

Which evidence suggests that several mass extinctions have occurred during Earth's history?

A
Fossils provide information about water level and temperature.
B
Many fossils demonstrate that organisms have changed over time.
C
Fossils of the same species have been found on distant continents.
D
Many fossils of organisms that are no longer living have been discovered.
16

Which unstable element is used to determine the age of volcanic rock?

A
argon
B
carbon-12
C
potassium
D
carbon-14
17

How did the formation of the ozone layer contribute to the existence of life on Earth?

A
It blocked the Sun’s harmful UV rays.
B
It caused water vapor to cool, condense, and collect.
C
It released large amounts of oxygen into the air.
D
It warmed Earth’s surface, preventing materials from freezing.
18

The image shows a fossil that is hard like rock but that resembles a tree.

Question illustration
A
This fossil reveals the activities of an organism.
B
This fossil was created in solidifying sediment.
C
This fossil is an impression left by an organism.
D
This fossil was an organism that has been turned into rock.
19

The diagram shows horizontal rock layers.

Question illustration
A
Layer C is the oldest layer.
B
Layer B is younger than layer D.
C
Layer C is older than layer A.
D
Layer D is the youngest layer.
20

Which statement explains one reason why unconformities occur?

A
Rocks along a fault break and move.
B
Igneous rock forms at Earth’s surface.
C
No sediment is deposited over a long time.
D
Igneous rock forms between sedimentary layers.

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