Which dating method relies on the position of rock layers
CC BY-SA 3.0], via Wikimedia Commons' src=" alt="The canyon is shown with many layers" width="3600" height="2400" srcset=" sizes="(max-width: 709px) 85vw, (max-width: 909px) 67vw, (max-width: 1362px) 62vw, 840px"/The Geologic Time Scale and the basic outline of Earth history were worked out long before we had any scientific means of assigning numerical units of age like years to events of Earth history.
Working out Earth history depended on realizing some key principles of relative time.
CC BY-SA 1.0], via Wikimedia Commons' src=" alt="" width="474" height="251" srcset=" sizes="(max-width: 474px) 85vw, 474px"/Relative time allows science to tell the story of the Earth, but does not provide specific numeric ages of events, and thus, the rate at which geologic processes operate.
Based on Hutton’s uniformitarianism, early geologists could surmise that geological processes work slowly and that the Earth is very old.
The specific events within Earth history are discussed in the Earth History chapter, Chapter 8.
Note that after about ten half lives, the amount of parent remaining is so small that chemical analysis of the parent is difficult and the accuracy of the method is diminished.
Ten half lives is generally considered the upper limit for use of an isotope An atom that has different number of neutrons but the same number of protons.
This is an example of the Principle of Lateral Continuity This image of Capitol Reef National Park from the ISS shows the Navajo Sandstone, a formation found throughout the western United States.
The rocks are a very light tan here, but can be a reddish color in places like Red Butte Garden in Salt Lake City or in Zion National Park.
GFDL, CC-BY-SA-3.0 or CC BY-SA 2.5-2.0-1.0], via Wikimedia Commons' src=" alt="Diagram showing the decay chain of several radioactive isotopes from radioactive parent isotopes to stable daughter isotopes.