As we all know, there are maps of many kinds. Most of us are familiar with maps that show us location of places, such as the map of the United States. However, other maps show other things. A geological map show where rocks and faults are at, as well as their location in an area. Then the map has various colors to show different information. It also includes many symbols. The geological map helps us to understand the earth beneath us, so we can understand the world around us better.
Notice the colored areas on this map taken from the US Geological Survey website. Each area is colored to match the type of geological unit (volume of a certain kind of rock of a given age range). For example, one area might be colored bright orange to show a sandstone of one age while another might be pale brown to show another sandstone of a different age.
The geologists name and define the geological units they find. They determine everything they do based on their findings of rocks and the ages of the rocks. These continue to change as more investigations are completed. The science of geology can be quite interesting.