Geologic Age Dating Explained - Kids Discover Geologic Age Dating Explained - Kids Discover

Radiometric dating practice worksheet for kids, you may also like

There are two basic approaches: Geologic age dating—assigning an age to materials—is an entire discipline of its own.

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Sedimentary rocks in particular are notoriously radioactive-free zones. Dinosaurs disappeared about 65 million years ago. How do scientists actually know these ages? For dating purposes, the important parameter is the half life of the reaction — the time it takes for half the material to decay.

There are a couple catches, of course. If a rock has been partially melted, or otherwise metamorphosed, that causes complications for radiometric absolute age dating as well.

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Radioactive materials can decay in any of several ways, emitting either a particle or radiation and changing to a different element or isotope. The decay rate of radioactive materials does not depend on temperaturechemical environment, or similar factors. But the most accurate forms of absolute age dating are radiometric methods.

Rubidum-Strontium dating is also popular. Take students on a neighborhood walk and see what you can observe about age dates around you.

Geologic Age Dating Explained

Have students work alone or in pairs to find an article or paper that uses radiometric age dating. Can you tell why? Pretty obvious that the dike came after the rocks it cuts through, right?

In a way this field, called geochronology, is some of the purest detective work earth scientists do. The decay product should not be a small-molecule gas that can leak out, and must itself have a long enough half life that it will be present in significant amounts.

This method works because some unstable radioactive isotopes of some elements decay at a known rate into daughter products. Most materials decay radioactively to some extent, but the decay rates of most are so long that, for all practical purposes, they can be considered inert.

Chart of a few different isotope half lifes: The procedures used to isolate and analyze the reaction products must be straightforward and reliable.

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Absolute age dating is like saying you are 15 years old and your grandfather is 77 years old. Geologists draw on it and other basic principles http: To determine the relative age of different rocks, geologists start with the assumption that unless something has happened, in a sequence of sedimentary rock layers, the newer rock layers will be on top of older ones.

Relative age dating also means paying attention to crosscutting relationships. Probably the best known form of radiometric dating is radiocarbon datingwhich uses carbon Say for example that a volcanic dike, or a fault, cuts across several sedimentary layers, or maybe through another volcanic rock type.

From the chart, which methods are best for older materials? Half lives of various isotopes vary from microseconds to billions of years. This is called the Rule of Superposition. Materials useful for radiometric dating have half lives from a few thousand to a few billion years.

Each radioactive isotope works best for particular applications.

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Here is an easy-to understand analogy for your students: You May Also Like. The remainder are said to be radioactive. Not all rocks have radioactive elements.

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No bones about it, fossils are important age markers. The half-life of carbon 14, for example, is 5, years.

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In addition, the initial element and the decay product should not be produced or depleted in significant amounts by other reactions. You might have noticed that many of the oldest age dates come from a mineral called zircon.

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In contrast to most systems, isochron dating[?