Relative dating determines the order in which a sequence of past events occurred, but does not determine exactly when the geologic events happened.
Absolute age determinations are numeric and identify when, in years, specific events happened.
Both techniques are important in different geologic situations.
Grand Canyon National Park [see Photo 1] is one of the best places in the world to gain a sense of geologic, or “deep,” time because the canyon exposes a great swath of geologic history.
Rocks exposed in Grand Canyon are truly ancient, ranging from 1840 million years old (m.y.), or 1.84 billion years old (b.y.), to 270 m.y.