Geologic History

Which process occurred most recently?

• formation of fault Y

• development of unconformity X

• formation of intrusion H

• deposition of rock layers D, E, and F

Layers of volcanic ash often serve as useful geologic time markers because ash layers usually

• deposit quickly over a wide area

• are older than the surrounding rock

• can be sampled easily

• darken with age

Which fossil appears to be the best index fossil?

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A fossil of which animal is most likely to be found in the bedrock of the Hamilton group?

• early reptile

• early dinosaur

• brachiopod

• human

Which index fossil has been found in Ordovician-age bedrock?

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A 65.5 million year old impact crater in Mexico provides evidence for the cause of the

• breakup of Pangaea

• evolution of the earliest corals

• Alleghenian Orogeny

• extinction of ammonoids

What is the approximate half-life of radioactive material X?

• 5,000 years

• 10,000 years

• 50,000 years

• 100,000 years

A bone sample contains only ¼ of its original radioactive C¹⁴ content. How old is the bone sample?

• 5,700 years

• 11,400 years

• 17,100 years

• 22,800 years

The diagram represents a sample of rubidium-87 (⁸⁷Rb). Which diagram represents the correct proportion of ⁸⁷Rb to its decay product, ⁸⁷Sr, after two half-lives?

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Rock layer X at location B is most likely the same relative age as which rock layer at location A?

• 1

• 2

• 3

• 4