Question

How are C-14 and U-238 dating used together in order to determine fossil ages?

Answer 1

Carbon 14 and Uranium 238 are not used together to determine fossil ages.

Carbon 14 with a half-life of 5,700 years can only be used to date fossils of approximately 50,000 years. Most fossils are thought to be much older than 50,000 years. Also, most fossils no longer contain any Carbon.

Uranium 238 has a half-life of 4.5 billion years. Uranium can be used to date the age of the earth.

Because of the huge differences in the half-lives of Carbon 14 and Uranium 238 they cannot be used together. Carbon 14 can only be used to date fossils of very recent age. Uranium 238 can only be used to date volcanic rocks of very old age.