Figure 4. Formation of coastal erosion features. Time 1: a small sea cave is eroded into rock along a vertical fracture. Old sea stacks exist seaward of the sea cliff; Time 2: Continued erosion of the sea cave develops a sea arch. The old sea stacks continue to erode from battering by wave-tossed boulders; Time 3: A new sea stack forms when the arch collapses, and a new sea cave begins to develop in a more landward location. The old sea stacks are worn down to a wave-cut platform. The time frame for this scenario varies with rock type and wave energy, but could require up to 500 years in Maine granite.
Last updated on October 6, 2005