Sedimentary rock is where aquifers are usually located.
Sedimentary rocks form under water. Sand, silt or some other material is deposited and then gets compressed by the layers of material on top, making rock. This sedimentary rock forms in layers. Scientists who want to know what the rocks are like under the ground take a core sample-they drive a hollow tube into the ground and then pull it up and look at the rock and material in the tube. Pour in 500 milliliters of dry sand.