These unusual tidal waves, so graceful in low light, are caused by a geological rarity at nearby Blue Hill Reversing Falls. In this country, only Maine has this kind of falls, and there are only eight of them in our State, according to the research.
Such falls occur when bedrock geology forms an inclined channel of a certain width and depth between two bodies of water, at least one of which is strongly tidal. There also must be the right height difference between the two bodies of water to produce rapid surges in rising and falling tides.
Apparently, during the last Ice Age, Maine’s coast was under a glacier cover longer than the coasts of more southern, smoother-coasted states. The moving ice here scoured the coast down to its granite bedrock, deposited boulders, and had a furious meltdown via rivers and other waterways that gouged geologic anomalies seen nowhere else.
(Brooklin, Maine)