Rock Layers and Geological Principles

How deep is the gorge carved by the Colorado River in some places?

• Less than a mile deep

• More than a mile deep

• Exactly one mile deep

• Half a mile deep

How old are some of the rocks exposed in the Grand Canyon?

• About 2 million years old

• About 200 million years old

• Almost 2 billion years old

• About 4.5 billion years old

How are rock layers formed?

• By volcanoes erupting

• By sediments like mud or sand being deposited and turning into rock over time

• By large earthquakes

• By glaciers moving across the land

What does the Law of Superposition state about rock layers?

• All rock layers are the same age.

• Younger layers are found below older layers.

• Younger layers form on top of older layers.

• Rock layers are always found in a random order.

If you hike down into the Grand Canyon, where would you find the oldest rock layers?

• At the very top of the canyon

• In the middle of the canyon walls

• At the bottom of the canyon

• They are scattered randomly throughout the canyon

What does the Law of Original Horizontality tell us about how rock layers are first formed?

• They are originally deposited flat.

• They are always formed in a U-shape.

• They are formed vertically.

• They are always formed at an angle.

What can cause rock layers to change their original flat shape?

• Only wind erosion

• Forces within the Earth like bending or uplifting

• Only water flowing over them

• The sun's heat

What does the Law of Cross-Cutting Relationships mean for rock layers?

• Rock layers are always younger than anything that cuts through them.

• Rock layers are older than anything that has happened to them.

• All rock layers are formed at the same time.

• Only faults can change rock layers.

What does the Law of Lateral Continuity suggest about rock layers found on opposite sides of a canyon?

• They are always different ages.

• They were formed by different sources.

• They were formed at the same time by the same source.

• They have no relation to each other.

What kind of information can geologists learn by studying rock layers?

• Only the color of ancient plants.

• How old rocks and fossils are, what the environment was like, and ancient climate.

• Only the types of minerals found in the rocks.

• How fast rivers used to flow.