Review Rock Layers and Fossils

The K-Pg Boundary was once called the K-T Boundary. It is a thin layer of rock found all over the world.

What event has evidence provided by the K-Pg Boundary?

• the mass extinction of dinosaurs

• ice sheets building up over the land

• the spread of early humans out of Africa

• the arrival of organisms on land

Scientists discover fossils of many land animals and plants in a layer of rock. Then beneath this layer, they discover fossils of fish, corals, and other marine animals.

What conclusion supports this evidence?

• The region had been dry land, and later was underwater.

• The region had both dry land and bodies of water, such as lakes and rivers.

• The region had been underwater, and later was dry land.

• The region was once along an ocean coastline.

A scientist discovers a fossil of a trilobite in a rock layer. Trilobites are examples of index fossils.

How is the discovery useful?

• It shows where other trilobite fossils can be found.

• It helps date the rock layer.

• It suggests that more fossils exist in deeper rock layers.

• It provides evidence that trilobites are alive today.

A thin, diagonal crack appears across the horizontal rock layers of a hillside. The rock layers are slightly higher on one side of the crack.

What is the most likely explanation for this observation?

• A strong earthquake separated the rock layers along the crack.

• Igneous rocks intruded into the rock layers along the crack.

• The rock layers formed after a strong earthquake occurred.

• The rock layers formed after a volcanic eruption formed the crack.

Scientists have concluded that strong tectonic forces can deform rock layers and move rocks across Earth's surface.

What evidence supports this conclusion?

Select the three correct answers.

• Fossils of the same species have been found on opposite sides of the Atlantic Ocean.

• Matching rock layers have been found on separate continents.

• Opposite walls of a canyon have matching rock layers.

• Barren mountains often reveal patterns of curved or tilted layers.

A science student is studying a canyon. The student states that the canyon formed over many years because of the weathering and erosion from a river.

Which observation would provide the strongest evidence for the student's statement?

• Opposite walls of the canyon have matching rock layers.

• Opposite walls of the canyon have rock layers that do not match.

• One wall of the canyon is slightly taller than the other wall.

• A highway was built along the floor of the canyon.