Radioactive Decay

Multiple Choice

How have scientists been able to determine the ages of rocks in the Grand Canyon?

• Using fossil records found in the rocks
• Scientists determine the ages of rocks in the Grand Canyon using radiometric dating techniques.
• By analyzing the color of the rocks
• Through visual inspection of rock layers

Multiple Choice

How can the half-life of a radioisotope be used to date a rock?

• The half-life of a radioisotope is irrelevant to geological dating.
• The half-life indicates the total age of the rock directly.
• The half-life of a radioisotope can be used to date a rock by measuring the ratio of isotopes and calculating the time elapsed based on the number of half-lives.
• Half-lives can only be used for dating organic materials.

Multiple Choice

 Why can’t carbon-14 dating be used to date specimens older than about 60,000 years?

• Carbon-14 dating relies on the presence of other isotopes for accuracy.
• Carbon-14 dating is effective for dating fossils and rocks.
• Carbon-14 dating cannot be used for specimens older than about 60,000 years due to the negligible amount of carbon-14 remaining.
• Carbon-14 dating can be used for specimens up to 100,000 years old.

Multiple Choice

What is radioactive dating?

• A method for measuring temperature changes in rocks.
• A process for identifying minerals in soil samples.
• A technique for predicting future geological events.
• Radioactive dating is a technique for determining the age of materials using the decay rates of radioactive isotopes.

Fill in the Blanks

Which radioisotope in the Table could you use to date a fossil thought to be about 500 million years old? Explain your choice.

Fill in the Blanks

Why does the amount of carbon-14 in an organism remain the same throughout the organism’s life? Why does the amount change after the organism dies?