This is the major flaw in radiometric dating, e. Sometimes, scientists already know the age of the fossil because fossils of the same species have been found elsewhere and it has been possible to establish accurately from those when the dinosaur lived. Accumulating Glitches. Using these methods, we've even been able to figure out the age of the Earth itself: Use of Index Fossils A related method we use to date rock is the use of reference fossils. The Earth's magnetic field has reversed many times during its history.
Fossils can help to match rocks of the same age, even when you find those rocks a long way apart.
Create a Goal Create custom courses Get your questions answered. These isotopes have longer half-lives and so are found in greater abundance in older fossils. Some of those elements are stable, and some are radioactive unstable. In an undisturbed sequence of rocks, such as in a cliff face, it is easy to get a rough idea of the ages of the individual strata — the oldest lies at the bottom and the youngest lies at the top. In each element, the number of protons is constant while the number of neutrons and electrons can vary. An example of this is given in Figure 8.