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

• era
• age
• half-life
• eon

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

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

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

What element is usually used to date fossils?

• uranium-235
• carbon-14
• mercury-203
• thorium-234

How old is the Earth?

• 4.6 billion years
• 1.4 billion years
• 4.6 million years
• 6000 years

The % of the parent isotope remaining after 1 Half Life.

• 50%

• 25%

• 12.5%

• 6.25%

What is the half life of Carbon-14?

• 5730 yrs

• 1.2 billion years

• 713 million years

• 1.3 billion years