Both hard rocks and soft rocks are found near the surface of the earth. Where water flows over harder rocks it may break through and wear away the softer underlying rocks. The hard rock then forms a shelf and, as a stream moves over the edge of this overhanging rocks, a WATERFALL is created. Pieces of this overhanging ledge may crack off and drop to the lower valley as is shown in this picture of the word-famous Niagara Falls, New York. Here horizontal strata of rocks stand out in bold relief from the vegetation and foaming water