Earth History Unit Review

Which is an example of absolute age?

• "This trilobite is older than that dinosaur."

• "That stromatolite is the absolute oldest fossil I've ever seen."

• "Velociraptors lived 71-75 million years ago."

• "The oldest sedimentary layer is on the bottom."

The half-life of a radioactive substance depends on the

• pressure acting on the material.

• amount of the material.

• temperature of the material.

• composition of the material.

Tags

NGSS.HS-PS1-8

A whale bone that originally contained 200 grams of radioactive carbon-14 now contains 25 grams of carbon-14. How many half-lives have passed since this whale was alive?

• 1

• 2

• 3

• 4

If carbon-14 is heated, the length of its half-life period would

• increase

• decrease

• remain the same

Tags

NGSS.HS-PS1-8

Carbon-14 can only be used to determine the age of

• recently living things (thousands of years old).

• recent rocks (thousands of years old).

• very old fossils (millions of years old).

• very old rocks (millions of years old).

Figure A and B represent the same radioactive substance. Compared to the half-life of the material in figure A, the half-life of the material in each small cube in figure B is

• 1/8 as long

• 8 times longer

• 1/64 as long

• the same

How much of the Earth's original U-238 still exists today?

• 100%

• 75%

• 50%

• 25%

Tags

NGSS.HS-PS1-8

What is the approximate age of an igneous rock that contains only one-fourth of its original potassium-40 content due to radioactive decay?

• 1.3 x 10⁹ years

• 3,9 x 10⁹ years

• 2.6 x 10⁹ years

• 5.2 x 10⁹ years

Compared to the length of time for the first half-life of a sample of a radioactive isotope, the length of time for the second half-life is

• less

• greater

• the same

Tags

NGSS.HS-PS1-8

What happens to a carbon-14 atom that has gone through radioactive decay?

• It disappears.

• It turns into nitrogen-14

• It becomes soil.

• It flips over so the radioactive side is face-down.