[Illustration: FIG. 265.—Cross section of a barrier beach with lagoon in its rear.]
=A barrier series.=—The cross section of a barrier beach, like that of a storm beach upon the shore, slopes gently upon the forward side, and more steeply at the angle, of repose upon the rear or landward margin (Fig. 265). The thinning wedge of shore deposits which the barrier throws out to seaward raises the level of the lake bottom (Fig. 266), and when coast irregularities are favorable to it, new spits will develop upon the shore outside the earlier one, and a new bar, and in its turn a barrier, will be found outside the initial one, taking a course in a direction more or less parallel to it (Fig. 267).
[Illustration: FIG. 266.—Cross section of a series of barriers and an outer bar.]
FIG. 267.—Formation of barrier series and an outer bar in University Bay of Lake Mendota, at Madison, Wisconsin. The water contour interval is five feet, and the land contour interval ten feet (based on a map by the Wisconsin Geological Survey).]
[Illustration: FIG. 268.—Series of barriers at the western end of Lake Superior (after Gilbert).]
So soon as the first barrier is formed, processes are set in operation which tend to transform the newly formed lagoon into land, and so with a series of barriers, a zone of water lilies between the outer barrier and the bar, a bog, and a land platform may represent the successive stages in this acquisition of territory by the lands. A noteworthy example of barrier series and extension of the land behind them, is afforded by the bay at the western end of Lake Superior (Fig. 268).
[Illustration: FIG. 269.—Character profiles resulting from wave action upon shores.]
=Character profiles.=—The character profiles yielded by the work of waves are easy of recognition (Fig. 269). The vertical cliff with notch at its base is varied by the stack of sugar-loaf form carved in softer rocks, or the steeper notched variety cut from harder masses. Sea caves and sea arches yield variations of a curve common to the undercut forms. Wherever the materials of the shore are loosely consolidated only, the sloping cliff is formed at the angle of repose of the materials. The barrier beach, though projecting but a short distance above the waves, shows an unsymmetrical curve of cross section with the steeper slope toward the land.