Because of the short length of the carbon-14 half-life, carbon dating is only accurate for items that are thousands to tens of thousands of years old. Most rocks of interest are much older than this. Geologists must therefore use elements with longer half-lives.

Why is carbon dating analysis is not always possible?

But scientists have long recognized that carbon dating is subject to error because of a variety of factors, including contamination by outside sources of carbon. Therefore they have sought ways to calibrate and correct the carbon dating method.

Why is carbon dating not often used for dating rocks?

Carbon dating cannot be used on most fossils, not only because they are almost always too old, but also because they rarely contain the original carbon of the organism. Also, many fossils are contaminated with carbon from the environment during collection or preservation proceedures.