<P> The sedimentary rock cover of the continents of the Earth 's crust is extensive ( 73 % of the Earth 's current land surface ) , but the total contribution of sedimentary rocks is estimated to be only 8 % of the total volume of the crust . Sedimentary rocks are only a thin veneer over a crust consisting mainly of igneous and metamorphic rocks . Sedimentary rocks are deposited in layers as strata , forming a structure called bedding . The study of sedimentary rocks and rock strata provides information about the subsurface that is useful for civil engineering , for example in the construction of roads , houses , tunnels , canals or other structures . Sedimentary rocks are also important sources of natural resources like coal , fossil fuels , drinking water or ores . </P>
what type of rock dominates the earth 's surface
sedimentary rock