Chapter 22 Review

Chapter 22 page 598

1. What is the commonly accepted age of Earth?

a) 4.6 Billion years

2. Which of the following was not a source of heat for the early Earth?

a) hydrothermal energy

3. What are small asteroids called?

a) meteoroids

4. What is the process by which a planet becomes internally zoned when heavy materials toward its center and lighter materials accumulate near its surface?

a) Diffentiation

5. Where is most of the North American Precambrian shield exposed at the surface?

a) Canada

6. What mineral can be used to radio metrically date Earth’s age?

a) zircon

7. Refer to Figure 22-6. What name is given to the core of the modern-day North American continent that formed in the Proterozoic?

a)Laurentia

8. What is the name of the first super continent which formed near the end of the Proterozoic?

a) Laurentia

9) What volcanic process most likely formed Earth’s atmosphere?

a) differentiation

10) Why is ozone a necessary component of Earth’s atmosphere?

a) It fillers out most of the sun’s UV radiation

11)Why is Earth’s atmosphere rich in nitrogen (N) and carbon dioxide (CO2) today?

a) because they can not escape Earth’s gravity

12) Rearrange the following phrases to create a cycle map that describes the formation of Earth’s early crust.

a) 1. upper mantle cooled and crystallized

2. sediments formed

3. sediments drawn down into subduction zones

4. Partial melting of sediments and subducted slab

5. Magma with new chemical composition formed

6. Granite crust formed as magma crystallized

7. Subduction continued forming more magma

8. crust weathered

13) Explain how geologists have determined the age of Earth?

a) Radio metric dating has determined that the ziron grans in the sedimentary rocks are between 4.1 and 4.2 billion years