Standard 9 Test Review

The bedrock cross section below contains rock formations A, B, C, and D. The rock formations have not been overturned. Which sequence represents the relative ages of these rock formations, from oldest to youngest?

• B→A→C→D

• B→D→C→A

• D→C→A→B

• D→B→A→C

The study of prehistoric life is called

• biology

• paleontology

• mineralogy

• geology

The dating method that determines the order of events, but not the actual dates of the events is called

• absolute dating

• radiometric dating

• relative dating

• radiocarbon dating

Base your answer to the following question on the diagram below which represents a cross section of an eroded fold that has not been overturned. The fossils found in rock layer G will most closely resemble those found in rock layer

• A

• I

• C

• D

The diagram below represents a cross-sectional view of a portion of the Earth's crust. Compared to the age of the sedimentary rock layers, the age of the igneous intrusion is

• younger

• older

• the same

Which radioactive substance would probably be used in dating the recent remains of a plant found in sedimentary deposits?

• carbon-14

• potassium-40

• rubidium-87

• uranium-238

Base your answer to the following question on the graph below and on your knowledge of Earth science. The graph shows the percentages of the radioactive isotope carbon-14 (14C) and its disintegration product produced during four half-lives of radioactive decay. How many half-lives have passed if a sample contains 25% of its original carbon-14?

• 1 half-life

• 2 half-lives

• 3 half-lives

• 4 half-lives

Base your answers to questions 13 and 14 on the graph below which shows the rate of radioactive decay of element A and the rate at which decay product B is formed. According to the graph, what is the total percentage of radioactive element A present after 3 half-lives?

• 12.5%

• 25.0%

• 75.0%

• 87.5%

The graph below shows the percent remaining (not decayed) of the original amount of carbon-14 at different times (A, B, and C) during radioactive decay. How many half-lives of time are represented by point B along the time axis?

• 1 half-life

• 2 half-lives

• 3 half-lives

• 4 half-lives

Why is carbon-14 not usually used to accurately date objects more than 50,000 years old?

• Carbon-14 has a relatively short half-life and too little carbon-14 is left after 50,000 years.

• Carbon-14 has a relatively long half-life and not enough carbon-14 has decayed after 50,000 years.

• Carbon-14 has been introduced as an impurity in most materials older than 50,000 years.

• Carbon-14 has only existed on Earth during the last 50,000 years.