How different types of sedimentary rocks are formed from clay, sand, pebbles and shells, by water, wind and pressure. Includes how sedimentary rocks are classified, how earth materials are carried by wind, water and ocean currents, how to distinguish between clastic and non-clastic sedimentary rocks, how cementing agents keep individual rocks together, how running water carries its load of rock particles, how geologists use sedimentary rock to study ancient life, and a look at evaporates such as salt and gypsum deposits.