Tidal Hell

In the days when the earth was young, the coming in of the tide must have been a stupendous event. If the moon was ... formed by the tearing away of a part of the outer crust of the earth, it must have remained for a time very close to its parent. It present position is the consequence of being pushed farther and farther away from the earth for some 2 billion years. When it was half its present distance from the earth, its power over the ocean tides was eight times as great as now, and the tidal range may even then have been several hundred feet on certain shores. But when the earth was only a few million years old, assuming that the deep ocean basins were then formed, the sweep of the tides must have been beyond all comprehension. Twice each day, the fury of the incoming waves would inundate the margins of the continents. The range of the surf must have been enormously extended by the reach of the tides, so that the waves would batter the crests of the high cliffs and sweep inland to erode the continents.

-- Rachel Carson, The Sea Around Us, 157-8