What is a relative dating technique
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.Sometimes sedimentary rocks are disturbed by events, such as fault movements, that cut across layers after the rocks were deposited.This is the principle of cross-cutting relationships.Layers of rock are deposited horizontally at the bottom of a lake (principle of original horizontality).Younger layers are deposited on top of older layers (principle of superposition).Second, it is possible to determine the numerical age for fossils or earth materials.
However, by itself a fossil has little meaning unless it is placed within some context.
In addition to being tilted horizontally, the layers have been faulted (dashed lines on figure).
Applying the principle of cross-cutting relationships, this fault that offsets the layers of rock must have occurred after the strata were deposited.
Most sediment is either laid down horizontally in bodies of water like the oceans, or on land on the margins of streams and rivers.
Each time a new layer of sediment is deposited it is laid down horizontally on top of an older layer.