Absolute dating places events or rocks at a specific time.If a geologist claims to be younger than his or her co-worker, that is a relative age.Geochronology is the science of dating and determining the time sequence of events in the history of the Earth.This web page provides an overview of selected geochronology methods used by USGS scientists.New dating methods are invented all the time, however, most have practical limitations.Geologic research and mapping requires the determinations of the ages and composition of rocks.If a geologist claims to be 45 years old, that is an absolute age.
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.
Seriation uses the assumption that once a tool was developed, its use would become more widespread.
Stratigraphy uses the assumption that higher layers or strata were laid down after lower layers.
Ice cores showed the age of a military plane buried in the artic as thousands of years old.
Similarly, dendrochronology measures the tree rings in trees and assumes they represent years.
It only sequences the age of things or determines if something is older or younger than other things.