Rock Dating

Which of the following is NOT an example of relative dating?

• Rock layers G is older than rock layer F.

• Rock layers C through G were folded after they formed.

• Rock layers B is 270 million years old.

• Rock layers A and B formed after rock layers C through G were folded.

Answer explanation

Relative dating compares the ages of rocks but doesn't give them an exact age.

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NGSS.MS-ESS1-4

Absolute dating is when...

• you assume rocks form in horizontal layers.

• you assume deeper layers of rock are older that the layers above them.

• you analyze a rock to determine its actual age (like 300 million years old).

• you assume that anything that cuts across rock layers is younger than the layers.

Answer explanation

Absolute dating gives a rock an actual estimated age, rather than just comparing it to other rocks.

We assume that rock layer C is older than rock layer B. Why?

• the law of original horizontality

• the law of cross cutting

• the law of superposition

• an index fossil

Answer explanation

The law of superposition says that lower layers of sedimentary rock are older that higher layers.

Tags

NGSS.MS-ESS1-4

Is D or E older?

• E is older

• D is older

• E and D are the same age

• We can't tell from this diagram

Answer explanation

D is older because it's an igneous intrusion that cuts across layer E.

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NGSS.MS-ESS1-4

What rule helps us determine that D is younger than E?

• The law of original horizontality.

• The law of superposition.

• The law of cross cutting.

• The presence of an index fossil.

Answer explanation

Cross cutting says that anything that cuts across a layer must be younger than what it cuts across.

Tags

NGSS.MS-ESS1-4

Is layer B or layer C older?

• layer B

• layer C

• they are the same age

• there is no way to tell from this image

Answer explanation

Layer C is older because it is below layer B

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NGSS.MS-ESS1-4

What rule tells us that layer C is older than layer B?

• the law of original horizontality

• the law of superposition

• the cross cutting law

• an index fossil

Answer explanation

The law of superposition says that a deeper layer of sedimentary rock is older that those above it.

Tags

NGSS.MS-ESS1-4

Which event happened first?

• Layers C through Y formed.

• Layers C through Y were tilted

• Layers H and N formed

• Intrusion R formed

Answer explanation

Layers form horizontally, so C through Y formed and then were tilted.

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NGSS.MS-ESS1-4

What rule tells us that C through Y formed and then were tilted?

• the law of original horizontality

• the law of superposition

• the cross cutting law

• index fossils

Answer explanation

The law of original horizontality tells us that sedimentary rock layers form horizontally, so if they are tilted that happened after they formed.

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NGSS.MS-ESS1-4

Choose ALL of the true statements about these rock layers containing fossils.

• The fossils in layer B are older than the fossils in layer A.

• Rock layer B is missing from location 4.

• The rock at location 1 has undergone more weathering than the rock at location 3.

• Layers A through D represent layers of sedimentary rock.

Answer explanation

Rock layer B is missing. It either didn't form in that location or it formed and water weathered away. Fossils are only found in sedimentary rock.

Tags

NGSS.MS-ESS1-4

NGSS.MS-LS4-1