Half life radioactive fossil dating
Ammonites, shelled relatives of today’s octopus, make ideal index fossils.
Suppose a dinosaur fossil has been found in the beds of an ancient delta (the mouth of a river leading to the sea).
After another half-life has passed, it will have decayed to an eighth, and so on. The half-life of potassium-40 is 1,310 million years, after which half of its substance will have changed into stable argon-40.
As soon as a living organism dies, it stops taking in new carbon.
After another 86 minutes, half of the 5 grams of Barium-139 would decay into Lanthanum-139; you would now have 2.5 grams of Barium-139 and 7.5 grams of Lanthanum-139.
The half-lives of certain types of radioisotopes are very useful to know.
The Age of Dinosaurs was so many millions of years ago that it is very difficult to date exactly.
Scientists use two kinds of dating techniques to work out the age of rocks and fossils. This considers the positions of the different rocks in sequence (in relation to each other) and the different types of fossil that are found in them.
Half-lives for various radioisotopes can range from a few microseconds to billions of years.The second method is called absolute dating and is done by analysing the amount of radioactive decay in the minerals of the rocks.Scientists find out the age of a dinosaur fossil by dating not only the rocks in which it lies, but those below and above it.The use of various radioisotopes allows the dating of biological and geological samples with a high degree of accuracy.
However, radioisotope dating may not work so well in the future.The ratio of carbon-12 to carbon-14 at the moment of death is the same as every other living thing, but the carbon-14 decays and is not replaced.