Question #4817e

1 Answer
Mar 18, 2017

Carbon 14 is the only radioactive method that is directly linked to fossils. It's half life is well known. The ratio of # C^14# to normal # C^12# is not affected by erosion.

Explanation:

Fossils are found almost exclusively in sedimentary layers. Uranium , Potassium and other radioactive dating methods are found only in igneous rocks. This makes it impossible to used radioactive dating to directly date the fossils found in sedimentary layers.

Radioactive methods like Uranium/ lead are subject to distortion due to erosions. Uranium is much more soluble than lead. So if the sample has been subjected to erosion the amount of Uranium will be less than the what the ratio should be. This will give a ratio that results in a age much longer than the what the age actually should be.

The problems with Carbon 14 dating is that because of its relatively short half life of only 5,700 years it can not be used to date fossil much more than 50,000 years. Also fossils often do not contain Carbon. The Carbon has been replaced by minerals as in fossilized wood. There is no carbon left in a mineralized fossil so Carbon 14 dating can not be used.