Relative absolute dating differences
Geologists have established a set of principles that can be applied to sedimentary and volcanic rocks that are exposed at the Earth's surface to determine the relative ages of geological events preserved in the rock record.
For example, in the rocks exposed in the walls of the Grand Canyon (Figure 1) there are many horizontal layers, which are called strata.
The principle of superposition states that in an undeformed sequence of sedimentary rocks, each layer of rock is older than the one above it and younger than the one below it (Figures 1 and 2).
Accordingly, the oldest rocks in a sequence are at the bottom and the youngest rocks are at the top.
Third, magnetism in rocks can be used to estimate the age of a fossil site.
This method uses the orientation of the Earth's magnetic field, which has changed through time, to determine ages for fossils and rocks.
The study of strata is called stratigraphy, and using a few basic principles, it is possible to work out the relative ages of rocks.
Younger layers are deposited on top of older layers (principle of superposition).This is the principle of original horizontality: layers of strata are deposited horizontally or nearly horizontally (Figure 2).