Absolute Dating By: Leticia Ruvalcaba, Jason Diego, Sierra Enciso

Key Concept Because radioactive decay happens at a constant rate, the age of a rock can be estimated by analyzing the amounts of different isotopes in a rock.

Vocabulary Absolute dating - a method of measuring the age of an object in years. Radioactive decay- the process when a radioactive isotope breaks down into a stable isotope of the same element or another element. Radiometric dating- a,method used to find the age of an object by estimating about the percentages of a radioactive isotope. Half-life - the time needed for half of a radioactive isotope to break down to form a daughter isotope.

Radioactive Decay Atoms of the same element that have the same number of protons but not the same number of neutrons are called isotopes. Most types of isotopes are stable but some are unstable. Isotopes that are unstable are called radioactive.

Dating rocks-parent and daughter isotopes Unstable radioactive isotopes are called parent isotopes. A stable isotope created by radioactive decay is called a daughter isotope. To date rocks scientist compare the amount of parent isotopes with the amount of daughter isotopes. If there are more daughter isotopes then the rock is older. If there are more parent isotopes then the rock is younger.

Radiometric dating If you know the rate of decay on a rock then you can determine the age of a rock. If a rock contains a half life of ten thousand years then after ten thousand years half the parent material would have decayed and become daughter material.

Using Radiometric dating Based on an estimated age of a sample scientists use different radiometric techniques. Isotopes with long half-lives can be used to date old rocks but not young rocks. Because younger rocks do not contain enough daughter material to allow even measurements.

Method of radiometric dating Potassium-40 has a half-life of 1.3 billion years. Its decays to argon and calcium. Geologists measure argon as daughter material. This method can be used to date rocks older than 10,000 years.

The age of our solar system Radiometric dating can be used to find the age of Earth. Rocks on earth are not as old as the earth because they have been recycled by plate tectonics. But other bodies in space contain rock that is as old as our solar system. The earth and the solar system is about 4.6 billion years old.

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