BEACHES, RAISED. Tracts of ground at various elevations above the present sea or lake levels, which have evidently been beaches at some former time. Such raised beaches owe their pres ent position to earth movements, which may have taken place rapidly, in connection with earth quakes, or more slowly, as part of the general system of changes attending the development of the earth's surface. At the present time, wher ever the ocean waves and surf are acting upon the bolder headlands of islands or continents, it is found that the (l kris is being carried seaward, ''„ and that a comparatively smooth floor is being formed over a belt of variable extent lying below the sea-level. If this contingent should rise sud denly, it would be recognized as a terrace of raised beach. The characteristics of such beaches I are: First, the nearly uniform elevation of the level terrace running approximately parallel to the present shore line; second, the presence of beds of water-worked sand and gravel; third, the presence in the beds of marine or fresh water shells belonging to species that were living at the time the sand was underneath the water. In America such raised beaches have been found around the coast of Ataine. on the coast of California and its adjoining islands, along the west coast of South America, and around the shores of many fresh-water lakes, and of the Great Salt Lake.
In Scotland a terrace extends around the bold coast of the west highlands and the western islands at an elevation of about twenty-five feet above present sea level. The famous parallel Roads of Glenroy extend on each side of the Val ley of the Roy. the first pair at an elevation of 1139 feet, the second of 1060 feet, and the third of 948 feet, above sea-level. These were origi nally supposed to be raised marine beaches, but • are now considered as beaches cut by the waters of a lake which once filled the valley.
The most interesting raised beaches are those surrounding the Great Lakes of North America. A careful survey of these beaches, made by 11r. 0. K. Gilbert. has shown that they are at present not absolutely horizontal, but rise as much as five feet per mile as one proceeds northward and eastward; further, the southern shores of the present lakes show a distinct tendency to flood ing or drowning. These facts lead to the conclu sion that the whole plain bearing the Great Lakes is being tilted, rising toward the northeast (north 27 degrees east) and sinking toward the southwest.