A bunch of boulders about four feet down on the bottom of the Bay

Clearing early, then sunny with a few puffs of cumulus. High of 19. We put up battens in the morning, but by afternoon we had to get outside. It being the Victoria Day long weekend we took a brief trip to the village to see what was happening, which turned out to be not much, although the Falls might have been hopping, for all we know. We walked with Pax along Fraser Beach, which is now so narrow that two people might find it difficult to walk side-by-side. Back at the cottage we launched the kayaks—or at least one of them—the plastic boat, which was outside all winter, was well occupied by a colony of ants. So, pending removal, we turned to the Susie P instead. I was thinking of titling this blog: "The Ants In Her Pants."

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The Benjamin Islands were made by a volcano, I’ve always maintained. The circular structure, when you include Fox Island and Croaker Island, looks a lot like a caldera.

In talking about this with Murray, he remembered a reference in the Great Lakes Cruising Club Guide, and later he was able to dig out the passage from which the following info is extracted.

According to the Guide, the Benjamins were created by vulcanism and not a meteor impact, as some folks from Sudbury (which is a meteor creation) have proposed. But it is not a caldera either. Rather, it’s a pluton. A pluton is a dome of molten igneous rock that has bubbled up from a pool of magma far below. The Benjamins bubbled up about 1.5 million years ago and have been eroded down ever since, from a dome to what we have today.

Above is the result of an aeromagnetic survey. The magnetic contours match the physical topography closely, and form the shape of a dome. — Above is the result of an aeromagnetic survey. The magnetic contours match the physical topography closely, and form the shape of a dome.

Interestingly, Harbor Island, on the south side of Clapperton, is another pluton, although overlaid with limestone.