Lately we have been getting facts pointing to the “oceanic” nature of the floor of so-called inland seas. Through geological investigations it has been definitely established that in its deepest places, for instance, the Caribbean Sea and the Gulf of Mexico, the Earth’s crust is devoid of granite stratum. The same may be said quite confidently about the Mediterranean and the Black Sea. Could the interpretation of these data be that inland seas were the primary stage of the formation of oceanic basins?

The edge of the sea is a strange and beautiful place. All through the long history of Earth it has been an area of unrest where waves have broken heavily against the land, where the tides have pressed forward over the continents, receded, and then returned. For no two successive days is the shore line precisely the same. Not only do the tides advance and retreat in their eternal rhythms, but the level of the sea itself is never at rest. It rises or falls as the glaciers melt or grow, as the floor of the deep ocean basins shifts under its increasing load of sediments, or as the Earth’s crust along the continental margins warps up or down in adjustment to strain and tension. Today a little more land may belong to the sea, tomorrow a little less. Always the edge of the sea remains an elusive and indefinable boundary.