The two principals above are accurate, but due to tectonics the position and appearance can change. A deformation in the Earth's crust may cause layers to be turned upside down or to be folded and faulted. A fold is a bend in the layers of rock. Faults are breaks in rock layers. Dikes and sills may intrude into rocks over time.
Dikes are ingenious intrusions cutting across surrounding rock.
Sills intrude parallel to the pre-existing rock layers. Introduction to Earth Science Lab. Whether the rock is in sandstone, shale, or limestone, it is shown on these maps. It is very important that the content of the bedrock be known when building roadways, housing developments, and when laying underground pipe. When you are ready to build your dream home, look at a geologic map to determine the most stable location and a good site.