Why is carbon-14 not useful to date rocks?

Answer 1

Although radiocarbon dating provides a useful tool there are some things that may make an artifact unsuitable for this process.

• The artifact is made from the wrong type of material.

  Carbon dating relies on measurement of radioactive decay from carbon 14 isotopes, some materials naturally do not contain enough carbon to date them.

• Radiocarbon dating is a destructive process.

  In order to conduct dating on an artifact you need a sample of it. Although this sample may only need to be very small, some artifacts are too precious to damage in this way.

• There may not be enough of it.

  Even if the sample is suitable in every other way, if you don't have enough of it then you cant do the test. Modern methods mean you may only need tiny amounts of carbon from the sample (0.1g) but depending on how much carbon is naturally in the material, this may translate to a fair amount of the original artifact. Carbon dates from small amounts of material also tend to be less accurate, and ideally you want to run several tests to be sure.

• The artifact may be too old.

  Radiocarbon dating is only effective back to a certain point. Beyond this there may not be enough radioactivity left in the sample to measure it. Also, radiocarbon dates need "correcting" on a calibration curve to correct the discrepancy between the age given in radiocarbon years and actual calendar years. Beyond around 45,000 years ago this curve is not so effective, and the remaining carbon-14 in the sample may be too small to measure.

• The artifact may be too young.

  Radiocarbon dating relies on the exchange of carbon through the carbon cycle. Recent human activity has affected the amounts of carbon in the atmosphere making carbon dating far less effective more recently than the early 1700. This is because processes such as the release old carbon into the atmosphere through the burning of fossil fuels and atmospheric nuclear weapons testing have led to dramatic peaks and dips in the amount of carbon 14 in the atmosphere.

• The sample may be contaminated.

  Contamination may occur before or after sampling and cause errors in the date that is produced. For example, water can disolve and deposit organic material changing the isotope levels. However, in most cases this can be dealt with in the lab during the sample preperation process. Archaeologists also take steps when selecting and recovering samples to minimise this potential problem.

Answer 2

Life on earth is carbon based. Life forms here take in carbon and include it in their structure. Some of this carbon is carbon-14, and it is radioactive - it decays over time. And when the once-living tissue has its carbon-14 content compared to the 14C concentration in the atmosphere (assuming it's relatively constant) the age of the once-living thing can be determined based on how much or little 14C is there. Metal artifacts don't incorporate carbon in their structures like living things do, and the carbon-14 dating method won't work with them. Only the biologicals can be dated, and there is an upper limit on our ability to do that. Dating a living thing back 100,000 years by this dating method is not do-able. Materials this old or older are said to be C-14 dead. After 100,000 years, "all" the 14C has decayed and gone.

There are now a few laboratories which carry out radiocarbon dating on iron objects. This can be done because carbon can be incorporated from the fuel used in the smelting process. However this can only be done in a few cases and arguably the error margins would be such as to make the process not particularly useful.

Answer 3

Carbon has two stable isotopes, carbon-12 and carbon 13. There are also trace amounts of the unstable, radioactive isotope, carbon-14, with a half-life of 5730 years. Because half the amount of carbon-14 in a sample is lost each 5730 years, the age of a carbonaceous sample can be estimated quite accurately by the remaining proportion of carbon-14. Because the atmospheric production of of carbon-14 could vary over time, scientists have calibrated carbon-14 readings against calcium carbonate deposits, such as stalagmites, of known ages to ensure reliable estimates are possible over a wide range.

However, the remaining amount of carbon-14 becomes too small to measure accurately after about 60,000 years, and thus can not be used for fossil samples older than this. Many fossils are hundreds of thousands, and even millions of years old, so carbon-14 dating is not useful in dating them.

Answer 4

Carbon-14 is not the right way to date rocks. Let me explain why: Carbon-14 only works on organisms that take in carbon-dioxide( living things ). Living organisms breathe in oxygen as well as carbon-dioxide because it's in the air, just taking in more oxygen. But rocks doesn't TAKE IN air, oxygen, and carbon-dioxide. So carbon-14 dating cannot date rocks.

Answer 5

its halflife is much too short for material that old

Answer 6

For starters, its half-life is way too short for this purpose.