One would think that humanity’sMitchum Robert interest in the nature of sea-level (SL) variations is relatively recent, but in fact pondering the rock evidence and speculating about how the sea might have shifted in the past was an old contemplative pastime. One puzzle that must have intrigued many ancient keen-eyed observers—as they stumbled upon delicate shells of obvious marine origin embedded in the cliffs high up in the mountains—must have been their incongruous location. To a discerning mind the plausibilities would have unfurled like an ancient scroll: Had a cataclysmic deluge swept the marine life this far inland? Had the sea suddenly vanished? Or had the land itself risen from the deep? But to the casual eye, it would not be apparent that such events may have recurred, time and again, over millennia.