Earth's History Review

The age of a rock layer in relationship to other rock layers above or below it

• absolute age.

• comparative age.

• relative age.

• relational age.

The numeric age of an object is called

• relational age.

• comparative age.

• relative age.

• absolute age.

Carbon-14 is an isotope

• used to find the relative age of a rock

• used to date objects less than 70,000 years old.

• used to date objects more than 70,000 years old.

• that cannot be used to date objects.

Index fossils found in rock layers in different areas of the world indicate that the rock layers

• formed during the same period of time.

• formed during different periods of time.

• are still forming.

• never fully formed.

Almost all fossils are discovered in

• volcanic rock.

• metamorphic rock.

• igneous rock.

• sedimentary rock.

Organisms that formed index fossils

• lived during long spans of geologic time.

• lived during short spans of geologic time.

• were destroyed by igneous rocks.

• were destroyed by sedimentary rocks.

Why is radioactive decay used to determine the absolute age of rocks?

• Radioactive decay only happens in young rocks.

• Radioactive decay happens very quickly.

• Radioactive decay does not happen at a constant rate.

• Radioactive decay happens at a relatively constant rate.

How is radioactive decay used to determine the absolute age of rocks?

• parent to daughter ratios of a radioactive isotope are compared to find the number half lives a sample has undergone thus finding the age of the rock sample

• comparing layers of rock to layers of rock above it

• comparing layers of rock to layers of rock below it

• a radioactive isotopes half life is determined and any rock with that isotope is the age of year in the isotope’s half life.

How many half-lifes would be necessary for a sample of parent isotopes to decay to the point that only one-fourth of the sample is composed of parent isotopes?

• 1

• 2

• 3

• 4

In radiometric dating, scientists compare the proportion of a radioactive parent isotope to a stable

• mother isotope

• sister isotope

• daughter product

• child product