8-3 Absolute Dating

Why are isotopes with short half-lives not useful for dating very old rocks?

• because not enough of the parent isotope remains to measure accurately
• because not enough of the daughter product has formed to be detectable
• because neither the parent isotope nor the daughter product will be detectable
• because very old rocks would never have contained these isotopes

Scientists use radioactive decay to measure...

• relative time
• absolute time
• half-lives
• time of day

The length of time required for half of the radioactive atoms in a sample to decay is its...

• era
• age
• half-life
• eon

After four half-lives, what fraction of the original parent isotopes remain?

• 1/4
• 1/16
• 1/8

The original element that undergoes radioactive decay is known as the...

• daughter element
• half-life
• parent element
• carbon-14

How does absolute age differ from relative age?

• only absolute dating indicates which rock is older than another
• only absolute dating finds the age in years
• only relative dating finds the age in years

When an unstable radioactive atom decays, it usually turns into:

• a more stable atom
• a less stable atom
• the exact same atom but with less pure energy
• empty space

Radiometric dating is possible because the rates of decay of radioactive isotopes _____.

• change over time
• change from place to place
• are constant
• vary widely

The time it takes for 50% of the nuclei in a radioactive sample to decay to its stable isotope is called _____.

• the daughter product
• geologic time
• the half-life
• the half-time

Approximately how old are Earth and the solar system?

• 4.6 million years old

• 6.4 billion years old

• 4.6 billion years old

• 4.8 billion years old