Age dating sediments
The theory that the outer layer of the Earth (the lithosphere) is broken in several plates, and these plates move relative to one another, causing the major topographic features of Earth (e.g.
mountains, oceans) and most earthquakes and volcanoes.
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 basic outline of Earth’s history were worked out long before we had any scientific means of assigning numerical age units, like years, to events of Earth history.
Working out Earth’s history depended on realizing some key principles of relative time.
Many geological samples contain multiple parent/daughter pairs, so cross-checking the clocks confirms that radioisotopic dating is highly reliable.
Comparisons of carbon ages with tree-ring data and other data for known events have allowed reliable calibration of the radiocarbon dating method.CC0], via Wikimedia Commons' src=" alt="The graph gets progressively taller" width="300" height="300" srcset=" sizes="(max-width: 300px) 85vw, 300px"/An atom that has different number of neutrons but the same number of protons.While most properties are based on the number of protons in an element, isotopes can have subtle changes between them, including temperature fractionation and radioactivity.3.Using this time scale, geologists can place all events of Earth history in order without ever knowing their numerical ages.
The specific events within Earth history are discussed in Chapter 8.An atom that has different number of neutrons but the same number of protons.