According to the National Park Service, sedimentary rock forms when mud and sand are deposited into layers on the earth’s surface and later buried. The buried mud and sand is compacted by the weight of the overlying layers of earth until they harden and form solid rock.
Sedimentary rock gets its name from the natural sediments that are formed by weathering and erosion in an area. The sediments are then transported by water, wind, ice and glacier movements where they collect together. These rocks make up approximately 8 percent of the total volume of the earth’s crust, which also includes a variety of other rock-types including igneous and metamorphic rocks.