Numerical age dating
Further confusion arises when one publication or geologist says, for example, that the Kaibab Formation is 270 m.y. The same questions arise for the other rock units at Grand Canyon. This article will answer these questions by providing a short primer on geologic dating methods and how they were applied to Grand Canyon rocks.
In a way this field, called geochronology, is some of the purest detective work earth scientists do.There are younger geologic deposits in Grand Canyon too, such as the Ice Age fossils found in caves, a 1000-year-old lava flow in the western canyon, and even the debris flow deposits that continue form each year.Yet, it is the canyon’s rock walls that allow people to develop their greatest perspective on geologic time, because of these rocks’ immense age, their fossil record, and because these rocks formed in environments far different than those found in northern Arizona today.There are two basic approaches: relative age dating, and absolute age dating.Here is an easy-to understand analogy for your students: relative age dating is like saying that your grandfather is older than you.