Unit 6- Clues to Earth's Past 7th Grade Review-2024-2025

Fossils are preserved remains of organisms that lived long ago. According to the Law of Superposition, the rock layers that contain fossils should be far below Earth's surface. Which answer best explains why fossils are sometimes found at or near the surface?

• Fossils are less dense than rock, so they rise to the surface.

• Fossils are moved to the surface by other organisms.

• Sedimentary rock layers are relatively soft, and new fossils sink through upper layers into older, deeper layers.

• Some rock layers with fossils have been exposed because of different processes, such as faulting, folding, and weathering.

The diagram shows the folding of rock layers that occurs in the process of mountain building. Which layer in the diagram is the youngest?

• Layer L

• Layer M

• Layer N

• Layer Q

The rock layers that make up the Grand Canyon range in age from 2 billion to 230 million years. What would a scientist need in order to compare the absolute ages of rocks from two different parts of the canyon?

• the location of each rock

• the size and hardness of each rock

• the size of the crystals that make up each rock

• the amounts of radioactive elements in each rock

Many features of rocks offer clues to their ages. Which feature does NOT provide information about the age of a rock?

• the position of the rock relative to other rock layers

• the size of the crystals that make up the rock

• the radioactive elements within the rock

• the fossils found within the rock

How can scientists determine the relative age of a layer of rock above the layer with an index fossil?

• Scientists can infer that the presence of an index fossil means the layers are the same age.

• Scientists can infer that the rock layer containing the index fossil is younger than the rock layer above.

• Scientists can infer that the rock layer above the index fossil is younger than the rock layer containing the fossil.

• Scientists can infer that the absence of the index fossil in the layer above means that the rock layer is older than the layer containing the fossil.

Scientists can infer that the absence of the index fossil in the layer above means that the rock layer is older than the layer containing the fossil. If the geologist had found the rocks in a natural rock formation, which rock sample would most likely have been found closer to the surface?

• Sample A

• Sample B

• Sample C

• Sample D

Radiocarbon dating is used to determine the age of materials that contain carbon. Which choice below can be dated using radiocarbon dating?

• lava flows

• igneous rock

• organic matter

• metamorphic rock

A geologist studies the side of a mountain with many layers of Earth exposed. The geologist wants to know more about when a particular layer of sandstone formed. Which observation could be used to determine the age of the sandstone layer?

• The width of the layer of sediment

• The type of fossils in the sediment

• The amount of moisture in the sediment

• The color of the minerals in the sediment

Radiometric dating is used to determine the age of materials that are non-living. Which of the following statements best describes what is being determined when using radiometric dating?

• The amount of time that has passed since the material formed.

• The relative date that the fossil lifeform died.

• The physical properties of the material.

• The color, texture and chemical properties of the material.

The figure below shows a newly discovered index fossil. What happened that helped this fish become a fossil?

• It was eaten by scavengers and taken to the surface.

• It got exposed at the surface because of the drought period.

• It was subjected to extremely high temperatures and floated to the surface.

• It was covered quickly by sediment after it died and pushed up by folding.