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]).
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.
Reading References for Chapter XVIII
G. K. Gilbert. The Topographic Features of Lake Shores, 5th Ann. Rept. U. S. Geol. Surv., 1885, pp. 69-123, pls. 3-20; Lake Bonneville, Mon. I, U. S. Geol. Surv., 1890, Chapters ii-iv, pp. 23-187.
Vaughan Cornish. On Sea Beaches and Sand Banks, Geogr. Jour., vol. 11, 1898, pp. 528-543, 628-658.
F. P. Gulliver. Shore Line Topography, Proc. Am. Acad. Arts and Sci., vol. 34, 1899, pp. 149-258.