AnswersBiology VIA Fall 2026 Lstrangesdale.orgGeologic Time

Geologic Time — 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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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.
3

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.
4

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.
5

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.
6

Which feature causes a gap in the geologic record?

A
extrusion
B
fault
C
intrusion
D
erosion
7

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
8

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.
9

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.
10

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
11

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.
12

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.
13

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
14

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
15

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
16

Which correctly lists three materials that preserve soft tissues in fossils?

A
amber, minerals, and sediment
B
minerals, permafrost, and amber
C
permafrost, amber, and tar
D
sediment, minerals, and tar
17

Which best explains how gravity contributes to the formation of layers in protoplanets?

A
Gravity attracts materials and causes compaction, which produces heat and leads to the melting, sinking, and rising of materials.
B
Gravity causes materials to undergo radioactive decay, which produces heat and leads to the melting, sinking, and rising of materials.
C
Gravity absorbs heat, which cools materials and causes them to sink and rise.
D
Gravity releases heat into space, which cools materials and causes them to sink and rise.
18

Which phrase describes carbon-14 dating?

A
uses the rate at which nitrogen-14 decays into carbon-14
B
dates the remains of organisms to determine when they died
C
measures the number of unstable elements in ancient volcanic rocks
D
determines the age of ancient fossils older than 50,000 years old
19

Which phrase describes one characteristic of radioactive elements?

A
are produced in a laboratory
B
decay at a constant rate
C
have a consistent number of particles
D
release energy and particles to maintain radioactivity
20

Which part of an organism is preserved in cast and mold fossils?

A
skin
B
bone
C
muscle
D
soft tissue

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