Half life radioactive fossil dating
The sediment of this area was laid down after ammonite A appeared 199 million years ago, and before ammonite B became extinct 195 million years ago.This narrows the date of the delta beds to the four million years between these dates.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 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.Sometimes, scientists already know the age of the fossil because fossils of the same species have been found elsewhere and it has been possible to establish accurately from those when the dinosaur lived.
In an undisturbed sequence of rocks, such as in a cliff face, it is easy to get a rough idea of the ages of the individual strata – the oldest lies at the bottom and the youngest lies at the top.
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.
The carbon-14 decays with its half-life of 5,700 years, while the amount of carbon-12 remains constant in the sample.
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).