Most fossils are excavated from sedimentary rock layers.
Sedimentary rock is rock that has formed from sediment, like sand, mud, small pieces of rocks.
Eventually, they are compressed into sedimentary rock. It is made of strata, or layers. The layers that are farther down in the Earth are older than the top layers. Most sedimentary rock layers are buried under soil or other rocks. The easiest way to find fossils is to find exposed sedimentary rock outcroppings.