Radioactive dating corals

Posted by / 03-Aug-2020 02:18

Radioactive dating corals

“They got in touch with the local doctor and said, ‘Would you mind X-raying our coral slice?’” When the coral slices were put in the X-ray scanner, a distinctive series of light and dark growth rings became visible, reflecting the density of the calcium carbonate that made up the coral skeleton.As researchers refine the surprising methods available to extract this kind of information from coral skeletons, the advice for climatologists, geochemists and paleontologists who want to plumb the oceans’ past has increasingly become: Look to the cores.“I call them natural reef history books,” said Janice Lough, a climatologist and coral core expert at the Australian Institute of Marine Science.Strontium has several other isotopes that are stable and do not decay.The ratio of strontium to one of the other stable isotopes, say strontium, increases over time as more rubidium turns to strontium Rubidium has a larger atomic diameter than strontium, so rubidium does not fit into the crystal structure of some minerals as well as others.In nearly all of the dating methods, except potassium-argon and the associated argon-argon method, there is always some amount of the daughter product already in the rock when it cools.

It’s easy to forget that no one was even sure corals set down annual growth rings until the 1970s.Coral colonies are made up of soft-bodied animals called polyps, which (with the help of symbiotic algae) secrete thin layers of the mineral calcium carbonate.Over time, these annual layers accumulate one atop another in a hard mass that makes up the coral skeleton.By knowing how long it takes all of the sand to fall, one could determine how long the time interval was.Similarly, there are good ways to tell quite precisely how much of the daughter product was already in the rock when it cooled and hardened.

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The Hawaii researchers were curious to see whether coral skeletons near Enewetak would show evidence of this radioactivity.

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