Even if we know what type of rock a certain rock is, we aren’t able to identify how the rock formed. Using the principle of uniformitarianism, we will be able to see how the rock is formed. This principle states that if we can understand how a process happens now and we find evidence of the same process happening in the past then we can assume the process happened the same way in the past.
An example of the principle of uniformitarianism is using how sand dunes form in order to determine how sandstone rock formed. We can decipher how many other rocks form by using the same technique.