Relative Dating

Which phrase describes the absolute age of a rock?

• does not provide an exact age

• is the number of years since it formed

• is the age compared to other rocks around it

• indicates whether it is younger or older than the rocks above it

A geologist finds four layers of sedimentary rock. She determines that no geologic events have shifted the layers. She labels the layers A, B, C, and D from the top to the bottom.

Which statement about these layers is accurate?

• A is older than B.

• B is older than C.

• C is younger than A.

• B is younger than D.

According to the law of superposition, which statements are supported by the diagram? Check 3 that apply.

• Layer C is the oldest layer.

• Layer B is older than layer D.

• Layer C is older than layer A.

• Layer D is the youngest layer.

• Layer C is younger than layer B.

Which statements are accurate? Check 2 that apply.

• Layer C is younger than layer A.

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• Layer B is younger than layer A but older than layer D.

• Layer D has an older relative age than layer C.

• If a geologic event tilted these layers, layer B would no longer be the oldest.

• It is possible to determine the absolute age of layer C with the information given

A geologist finds some tilted sedimentary rock layers.

Which conclusions can the geologist draw by looking at the rock layers? Check 3 that apply.

• Their absolute age is 600 million years.

• They were tilted after they were deposited.

• They were originally deposited horizontally.

• The youngest layer was originally deposited as the bottom layer.

• Their relative ages have not changed even though they are tilted.

In which situations is the principle of cross-cutting relationships useful in determining relative age? Check 3 that apply.

• A fault breaks through sedimentary layers.

• Sedimentary layers form and then are tilted.

• Igneous rock forms between sedimentary layers.

• Sedimentary layers form over millions of years in a lake bottom.

• Lava flows form on top of one another from several eruptions over time.

Which characteristic is shared by extrusions, intrusions, and faults?

• All are cracks.

• All are igneous rocks.

• All cause gaps in the geologic record.

• All are younger than surrounding rocks.

Which feature forms at Earth’s surface from the cooling of lava?

• extrusion

• fault

• intrusion

• unconformity

Which statements describe formations 1 and 2? Check 3 that apply.

• Formation 2 is an intrusion.

• Formation 1 is an extrusion.

• Formations 1 and 2 are faults.

• Formations 1 and 2 are igneous rock.

• Formations 1 and 2 are the same age as the surrounding layers.

Which statements explain reasons why unconformities occur? Check 2 that apply.

• Rocks along a fault break and move.

• Igneous rock forms at Earth’s surface.

• Rocks erode and sediment is deposited.

• No sediment is deposited over a long time.

• Igneous rock forms between sedimentary layers.