Dating Fossils

Which fossil makes the best index fossil?

• ammonite

• brachiopod

• trilobite

• shark

• all four are good index fossils

Index fossils help determine relative age through correlating rock layers.

• True

• False

Tags

NGSS.MS-ESS1-4

Why is D younger than B?

• D had to be there for B to intrude

• D and B happened at the same time

• B was laid on top of D

• B had to be there for D to intrude

Tags

NGSS.MS-ESS1-4

Radioactive dating of fossils and rocks is possible because radioactive isotopes

• are found in all fossils and rocks

• are easily collected and measured

• disintegrate into organic substances

• disintegrate at a predictable rate

Tags

NGSS.HS-PS1-8

A fossil formed 11,400 years ago. Which percentage of the original amount of carbon-14 remains in the fossil?

• 100%

• 50%

• 25%

• 12.5%

Tags

NGSS.HS-PS1-8

A sample of wood that originally contained 100 grams of carbon-14 now contains only 25 grams of carbon-14. Approximately how many years ago was this sample part of a living tree?

• 2,850 years

• 5,700 years

• 11,400 years

• 17,100 years

Tags

NGSS.HS-PS1-8

How old is a bone that has 12.5% of the original amount of radioactive carbon-14 remaining?

• 5,700 years

• 17,100 years

• 11,400 years

• 22,800 years

Tags

NGSS.HS-PS1-8

How old is a fossil that has radioactively decayed through 3 half-lives of carbon-14?

• 5,700 years

• 17,100 years

• 22,800 years

• 28,500 years

Tags

NGSS.HS-PS1-8

Base your answer on the diagram, which represents a model of a radioactive sample with a half-life of 5000 years. The white boxes represent undecayed radioactive material and the shaded boxes represent the decayed material after the first half-life.

Which radioactive isotope has a half-life closest in duration to this radioactive sample?

• carbon-14

• potassium-40

Tags

NGSS.HS-PS1-8

Which of the following methods is commonly used to date fossils?

• Carbon dating

• Thermoluminescence

• Dendrochronology

• Potassium-argon dating