Answer:
law of superposition
Step-by-step explanation:
The law of superposition in geology suggests that the sediments are spreading out in a horizontal manner, flat, in all directions, until there's some natural feature that will stop them. It also suggests that the sediments are arranged vertically from the oldest being at the bottom, and the youngest layers being on the top.
Even though this is not always the case in nature, still there are lot of examples that support the law of superposition. When the sediments are aligned in that manner, the geologists find it very helpful and easy to determine the relative age of the layers, as well as the relative age of the fossils that are found in them.