Play a game that tests your ability to match the percentage of the dating element that remains to the age of the object.Read the passage in this science printable to learn about the history of radioactive dating and its uses.Like the other kind of dating, geologic dating isn’t always simple.

radiometric dating 7th grade-59

But the most accurate forms of absolute age dating are radiometric methods. Sedimentary rocks in particular are notoriously radioactive-free zones.

This method works because some unstable (radioactive) isotopes of some elements decay at a known rate into daughter products. Half-life simply means the amount of time it takes for half of a remaining particular isotope to decay to a daughter product. Good discussion from the US Geological Survey: geochronolgists just measure the ratio of the remaining parent atom to the amount of daughter and voila, they know how long the molecule has been hanging out decaying. So to date those, geologists look for layers like volcanic ash that might be sandwiched between the sedimentary layers, and that tend to have radioactive elements.

Pretty obvious that the dike came after the rocks it cuts through, right?

With absolute age dating, you get a real age in actual years.

For example, which is older, the bricks in a building or the building itself?

Are there repairs or cracks in the sidewalk that came after the sidewalk was built?

It’s based either on fossils which are recognized to represent a particular interval of time, or on radioactive decay of specific isotopes. Based on the Rule of Superposition, certain organisms clearly lived before others, during certain geologic times.

After all, a dinosaur wouldn’t be caught dead next to a trilobite.

On the other hand, the half-life of the isotope potassium 40 as it decays to argon is 1.26 billion years.

So carbon 14 is used to date materials that aren’t that old geologically, say in the tens of thousands of years, while potassium-argon dating can be used to determine the ages of much older materials, in the millions and billions year range.

Students will answer comprehension questions and solve word problems using a table with information about the half-lives of radioactive elements.