Relative Dating Practice

Scientific law that states in horizontal sedimentary rock, the oldest layers are at the bottom

• intrusion

• fault

• index fossil

• superposition

Answer explanation

The law of superposition states that in horizontal sedimentary rock layers, the oldest layers are at the bottom and the youngest are at the top. This principle helps geologists determine the relative ages of rock formations.

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NGSS.MS-ESS1-4

The diagram shows a cross section of rocks beside a highway. 
Which rock type is the oldest?

• rock type 1

• rock type 2

• rock type 3

• rock type 4

Answer explanation

In geological cross sections, the oldest rock is typically found at the bottom. Since rock type 4 is positioned lowest in the diagram, it is the oldest rock type among the options provided.

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NGSS.MS-ESS1-4

In the diagram which rock lasyer is probably the oldest?

• layer 1

• layer 2

• layer 5

• layer 6

Answer explanation

In sedimentary rock layers, the oldest layers are typically at the bottom. Since layer 6 is the lowest in the diagram, it is likely the oldest rock layer compared to layers 1, 2, and 5.

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NGSS.MS-ESS1-4

Which rock layer most likely contains fossils of the most recently evolved organisms

• 1

• 2

• 3

• 4

Answer explanation

Rock layer 1 is the most recent, containing fossils of the most recently evolved organisms. As layers form over time, the uppermost layers hold younger fossils, while deeper layers contain older organisms.

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NGSS.MS-ESS1-4

NGSS.MS-LS4-1

The diagram shows some of the layers of rocks found in the Grand Canyon. Scientists find these layers of rock useful for studying fossils
What type of rock is shown labeled in these layers?

• extrusive

• igneous

• metamorphic

• sedimentary

Answer explanation

The layers of rock in the Grand Canyon are primarily sedimentary. Sedimentary rocks are formed from the accumulation of sediments and are known for containing fossils, making them valuable for studying ancient life.

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NGSS.MS-ESS2-3

Which can most likely be concluded about the top layer of rock seen in an undisturbed cliff wall?

• The top layer is older than layers located farther down the cliff.

• The top  layer is younger than layers located farther down the cliff.

• The top layer contains more fossils than layers located farther down the cliff.

• The top layer contains fewer fossils than layers located farther down the cliff.

Answer explanation

In geology, the Law of Superposition states that in undisturbed layers of rock, the oldest layers are at the bottom and the youngest are at the top. Therefore, the top layer is younger than the layers located farther down the cliff.

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NGSS.MS-ESS1-4

The age of a rock compared to the ages of other rocks is the rock's

• absolute age

• geologic age

• sedimentary age

• relative age

Answer explanation

The relative age of a rock refers to its age in comparison to other rocks, indicating whether it is older or younger, rather than providing a specific numerical age. Thus, the correct answer is relative age.

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NGSS.MS-ESS1-4

A gap in the geologic record is known as a(n)_______________.

• unconformity

• intrusion

Answer explanation

A gap in the geologic record is called an unconformity. It represents a period where no deposition occurred, leading to missing layers of rock, distinguishing it from other geological features like intrusions.

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NGSS.MS-ESS1-4

The preserved remains of an organism from long ago is called a ___________

• stratum

• clast

• fossil

• relative age

Answer explanation

The preserved remains of an organism from long ago are called fossils. Fossils provide important information about past life forms and their environments, distinguishing them from terms like stratum or clast.

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NGSS.MS-LS4-1

Fossil #1 is found 700ft under ground and fossil #2 is found 300ft under ground, which is newer?

• Fossil #1

• Fossil #2

• Neither fossil is newer

• Both Fossils are the same age

Answer explanation

Fossils found deeper underground are generally older due to the layers of sediment that accumulate over time. Since fossil #1 is 700ft deep and fossil #2 is 300ft deep, fossil #2 is newer.

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NGSS.MS-ESS1-4