These standard calibration curves assume that at any given time radiocarbon levels are similar and stable everywhere across each hemisphere. While K-Ar dating requires destroying large samples to measure potassium and argon levels separately, Ar-Ar dating can analyze both at once with a single, smaller sample. This includes factoring in many variables, such as the amount of radiation the object was exposed to each year.
Often, archaeologists use graves and plant remains to date sites. This technique is widely used on recent artifacts, but teachers should note that this technique will not work on older fossils like those of the dinosaurs which are over 65 million years old. The ratio of carbon to carbon in the atmosphere and on earth is nearly constant, although there has been some change in carbon concentration over the last 10, years.