Q3 SW#5 Determining Ages of Rocks 5P

What is the Law of Superposition?

• The principle that in undisturbed horizontal sedimentary rock layers, the oldest layer is at the bottom and the youngest layer is at the top.

• The principle that the youngest rock layers are always on the bottom.

• The principle that all rock layers are the same age.

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NGSS.MS-ESS1-4

Which type of fossil is used to determine the relative ages of rock layers?

• Trace fossils

• Index fossils

• Petrified fossils

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NGSS.MS-ESS1-4

NGSS.MS-ESS2-3

Explain how geologists use the position of rock layers to determine their relative age.

• By measuring the thickness of each layer.

• By analyzing the color of the rock layers.

• By using the law of superposition to determine that the oldest layers are at the bottom and the youngest are at the top.

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NGSS.MS-ESS1-4

What is radioactive decay?

• The process by which rocks are broken down by weathering.

• The process by which unstable atomic nuclei lose energy by emitting radiation and changing into another atom.

• The process by which sedimentary rocks are formed.

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NGSS.HS-PS1-8

Describe how geologists use radioactive dating to determine the absolute age of rocks.

• By comparing the amount of a radioactive element in a rock sample with the amount of the stable element into which it decays, using the element's half-life.

• By measuring the thickness of the rock layers.

• By identifying the types of fossils found in the rock.

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NGSS.MS-ESS1-4

What is an unconformity in the geologic record?

• A continuous sequence of rock layers.

• A gap in the geologic record where rock layers have been lost due to erosion.

• A fold in the rock layers.

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NGSS.MS-ESS1-4

How do geologists use index fossils to match rock layers?

• By comparing the color of the rock layers.

• By identifying the presence of the same index fossils in different rock layers, indicating they are the same age.

• By measuring the thickness of the rock layers.

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NGSS.MS-ESS1-4

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What is the half-life of a radioactive element?

• The time it takes for half of the radioactive atoms to decay.

• The time it takes for a rock layer to form.

• The time it takes for a fossil to form.

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NGSS.HS-PS1-8

Why can't carbon-14 dating be used to date rocks older than about 50,000 years?

• Because carbon-14 is not found in rocks.

• Because the amount of carbon-14 left would be too small to measure accurately.

• Because carbon-14 decays too quickly.

What is the significance of an igneous intrusion in determining the relative age of rock layers?

• It is older than the rock layers it cuts through.

• It is younger than the rock layers it cuts through.

• It is the same age as the rock layers it cuts through.

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NGSS.MS-ESS1-4