Geologic Time Scale and Fossil Record

Scientists use unstable elements that decay, called _________ elements, to determine the actual age of a fossil.

• radioactive
• cation
• anion
• petrified 

What is the half-life of a radioactive element?

• How old it is when it is middle aged
• The time it takes for half of the atoms to decay
• The time it takes for half of the atom to form
• How old it is when the Earth is middle aged

The millions of fossils that scientists have collected are called

• The Geologic Time Scale
• The Origin of Species
• The Fossil Record
• A really neat fossil collection

What is a mass extinction?

• the extinction of all of Earth's species at ones time
• the extinction of many types of organisms at the same time
• the end of days
• the creation of many species at one time

Relative dating can only help scientists determine whether one fossil is older than another.

• True
• False

In layers of sedimentary rock, the _________ layer is usually at the bottom. Each higher layer is _________ than the layers below it.

• oldest, younger
• youngest, older
• youngest, younger
• oldest, older

By determining the age of fossils, scientists can reconstruct the history of life on Earth

• True
• False

Which of the following could form a fossil?

• Bone
• Shell
• Seeds
• All of the above

Organization of Earth's history

• rock record

• geologic time scale

• fossil record

• index fossil

the ACTUAL age

• absolute age

• absolute dating

• relative age

• relative dating