Geology Reference
In-Depth Information
Stratigraphic column showing the rock formations exposed in the walls of the Grand Canyon
(
based on a sketch by Véro-
nique Robigou
).
Uranium-lead dating is the radiometric method commonly used to date the oldest rocks.
The 4.47-billion-year half-life for the decay of uranium 238 (
238
U) to lead 206 (
206
Pb) is
about the planet's age. Zircon, an uncommon mineral found in rocks like granite, is ideal
for this dating method, as it strongly excludes lead from its structure upon crystallization.
