Fossil age is determined using two methods, relative dating and absolute dating. In relative dating, fossils are compared to similar fossils and rocks, the ages of which are known. Absolute dating, on the other hand is used to calculate the precise age of fossils through radiometric dating.

How can you tell how old a dinosaur fossil is?

There are two ways to determine the age of a dinosaur fossil. One is called relative geologic time, which involves deciding whether one dinosaur fossil is older or younger than another. The other is often called absolute geologic time, which involves estimating how many millions of years old a dinosaur fossil is.

How do we know fossils are millions of years old?

Fossils span geologic time from hundreds to even billions of years and are discovered in many rock types and settings. Another common method, uranium-lead dating, relies on the radioactive decay of uranium and can be used to date rocks containing the oldest known fossils on Earth—older than 3.5 billion years old!

How do we know dinosaurs existed millions of years ago?

To discover how organisms lived in the past, paleontologists look for clues preserved in ancient rocks—the fossilized bones, teeth, eggs, footprints, teeth marks, leaves, and even dung of ancient organisms. Fossilized jaws, teeth, and dung provide important clues about what non-avian dinosaurs ate.

How do scientists know how old a bone is?

Carbon-14 atoms decay at a constant rate, because they are radioactive. Scientists can then compare the ratio of normal carbon (carbon-12) to radioactive carbon-14 to determine an approximate age of the creature by testing and analyzing its ancient, fossilized bones.