Todays knowledge of fossil ages comes primarily from radiometric dating, also known as radioactive dating. Radiometric dating relies on the properties of isotopes. These are chemical elements, like carbon or uranium, that are identical except for one key feature -- the number of neutrons in their nucleus.

How do paleontologists date dinosaur fossils?

Because fossils are usually found in sedimentary rock layers, paleontologists can date them by examining the minerals above or below the sedimentary rock. Zircon, a mineral commonly found in igneous rocks, proves particularly useful. As zircon forms in cooling magma, its crystal structure contains uranium but no lead.

What do paleontologists use to date fossils?

radiometric dating The geological time scale is used by geologists and paleontologists to measure the history of the Earth and life. It is based on the fossils found in rocks of different ages and on radiometric dating of the rocks.

How do they date fossils?

To establish the age of a rock or a fossil, researchers use some type of clock to determine the date it was formed. Geologists commonly use radiometric dating methods, based on the natural radioactive decay of certain elements such as potassium and carbon, as reliable clocks to date ancient events.