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.
The study of strata is called stratigraphy, and using a few basic principles, it is possible to work out the relative ages of rocks.
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 age of the fossil must be determined so it can be compared to other fossil species from the same time period.
Understanding the ages of related fossil species helps scientists piece together the evolutionary history of a group of organisms.
However, the age of each fossil primate needs to be determined so that fossils of the same age found in different parts of the world and fossils of different ages can be compared.
There are three general approaches that allow scientists to date geological materials and answer the question: "How old is this fossil?The layers of rock at the base of the canyon were deposited first, and are thus older than the layers of rock exposed at the top (principle of superposition).In the Grand Canyon, the layers of strata are nearly horizontal.This is the principle of original horizontality: layers of strata are deposited horizontally or nearly horizontally (Figure 2).Thus, any deformations of strata (Figures 2 and 3) must have occurred after the rock was deposited.Archaeology is the scientific study of past human lives and activities through material objects.