Relative dating rock layers
This interactive asks you to use your knowledge of relative dating. Help us work out the relative ages of the layers of sedimentary rocks.
You need to work out the order in which rocks were formed, from youngest to oldest. Remember that younger sedimentary rocks lie on top of older ones and were horizontal when formed.
This follows due to the fact that sedimentary rock is produced from the gradual accumulation of sediment on the surface.
Therefore newer sediment is continually deposited on top of previously deposited or older sediment.
The first principle is the Principle of Superposition which states that in an undisturbed succession of sedimentary rock, the oldest layers are on the bottom.If conditions are right the remains of the dying organisms can then be preserved as fossils within the rock that formed from sediments that covered the remains.Since, all sedimentary rock is formed through the gradual accumulation of sediment at the surface over time, and since the principle of superposition tells us that newer sediment is deposited on top of older sediment, the same must also be true for fossils contained within the sediment.The principle of cross-cutting states that any geologic feature that crosses other layers or rock must be younger then the material it cuts across.