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The Sound of Science - 'Dating a mountain'


The Sound of Science - 'Dating a mountain'

Welcome to The Sound of Science from WNIJ and NIU STEAM. It’s a weekly series explaining important STEM concepts. Today’s hosts are Jeremy Benson and Newt Likier.

Today’s question comes from Matt, who wants to know how we can find out how old a mountain is?

You ask it politely, and then say it doesn’t look a day over thirty.

Or if you want to be all science-y about it you could utilize geochronology and measure the radiometric decay of the unstable isotopes in the mountain.

Just like carbon dating can be used to date organic samples, scientists can also use radioactive decay to date inorganic matter, like rocks and minerals.

Over time, uranium found in these samples will slowly decay into lead, so scientists look at the ratio of uranium to lead in the chemical makeup of a sample. This method is called Uranium-Lead Dating.

You may have heard the term half-life before. That refers to how long it takes for half of an unstable sample to decay. Scientists have already collected quite a bit of data on radioactive isotopes and their half-lives. Because we know those decay rates, we can use them to extrapolate the age of a sample.

Another method of determining a sample’s age is biostratigraphy. With biostratigraphy, scientists use context clues as a way to gauge an unknown sample’s age against other known samples.

In other words, a scientist might see a rock that is has very similar properties to another rock she knows is from the Jurassic Period. She could say, then, that the newly found rock is likely from the same time period as the Jurassic rock.

Biostratigraphy isn’t as precise, but both methods have their uses. And together, they can provide a fuller picture than either would alone.

Wow, geologists must have very busy social lives. They’re so preoccupied with dating!

(groan) Newt, that joke is so old you could uranium-lead date it.

If there’s anything you want to learn about the world, submit your questions to niusteam@niu.edu

This has been the Sound of Science on WNIJ. Where you learn something new every day.

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