Geologists use radiometric dating to estimate how long ago rocks formed, and to infer the ages of fossils contained within those rocks. Radioactive elements decay The universe is full of naturally occurring radioactive elements. Radioactive atoms are inherently unstable; over time, radioactive "parent atoms" decay into stable "daughter atoms. When molten rock cools, forming what are called igneous rocks, radioactive atoms are trapped inside.
Dating Fossils in the Rocks
DETERMINING AGE OF ROCKS AND FOSSILS
There are a lot of people who believe, unequivocally, that the ages scientists assign to all rocks and fossils are certain. It is declared:. The good dates are confirmed using at least two different methods, ideally involving multiple different independent labs for each method to cross-check results. Sometimes only one method is possible, reducing the confidence researchers have in the results. And the ugly dates?
Telling Time at Grand Canyon National Park
There are two types of age determinations. Geologists in the late 18th and early 19th century studied rock layers and the fossils in them to determine relative age. William Smith was one of the most important scientists from this time who helped to develop knowledge of the succession of different fossils by studying their distribution through the sequence of sedimentary rocks in southern England. It wasn't until well into the 20th century that enough information had accumulated about the rate of radioactive decay that the age of rocks and fossils in number of years could be determined through radiometric age dating.
Explore This Park. The eroded cliffs reveal 1. The oldest rocks exposed in the canyon are ancient, 1, million years old. Conversely, the canyon itself is geologically young, having been carved in the last 6 million years.