Theories and Marlinspike

Sloop Cove, Valcour Island
N 44 37.421 W 73 24.448

I found a number of additional holes dissolved in the limestone like the ones I discussed before. I can confirm that 100% of them are aligned with vertical cracks in the rock that extend down in to the water. I'll therefore assume that my speculation that they were formed by wave action as confirmed. If they were formed by dripping water from above, they would not all be aligned with the cracks.

I'll call them blow holes. I think that's what they are called when found in other places. A famous one comes to mind from Acadia National Park in Maine. There, the waves are much bigger and the hole more spectacular, but the principles are the same. Blow holes they are.

Libby and I have spent a lot of time on Valcour Island, including numerous times when the weather could be described as heavy and when the waves crash on to the shore side rocks and cliffs. Yet we've never observed water jetting up through one of these blow holes. So, if it doesn't happen then; when? I'll speculate further.

Lake Champalain freezes over from shore to shore only once every 10 years or so. Still, every year the bays freeze and the shore lines acquire an apron of ice extending from the shore out into open water. What happens when waves in the open water encounter such an apron of ice. It seems reasonable to assume that the wave action is transferred to pressure waves in the water beneath the ice. If the ice is thin or consists of a broken ice pack, then the vertical wave motion may even be visible on
the ice. As the ice gets thicker, the vertical motion would be suppressed and the pressure waves in the incompressible water below would be magnified. When the pressure wave reaches the shore, its forward progress is stopped and reflected by the unyielding rocks. That acceleration on top of the pressure wave would result in a concentrated pressure pulse.

Suppose now that the pulse is focused in the water lying in one of the dead end vertical cracks at the shore. The focus would become even sharper. It should shoot a jet of water upward through the crack. If that happened repeatedly the walls of the crack would become coated with ice and would eventually close off. At some point, only a few, or perhaps only one path may remain for the high pressure water pulse to come up to the surface. If that was true, the pressure waves would result in very
high pressure high speed jets of water being forced up through the remaining opening. Under those conditions, I could understand how the holes in the rock might be formed in a few days. Millions of years would not be required.

If my speculation is correct, the jets of water on Valcour Island's shores would be like mini geysers in the winter. The water streaming out would build up ice in a cone like formation surrounding the hole. They would then come to resemble mini volcanos with surrounding cinder cones.

We have never been to Valcour in the winter, so I can't say if my speculation is correct. If any readers have other theories or ideas as to how we could verify this idea, please let me know.

Yesterday was a very nice day to sail but we elected to tackle a project that has been waiting for a long time. Last spring, when anchored at Key Biscayne near Miami, we were hit by an unexpected severe thunderstorm at 1000 in the morning. Winds rose to 65 knots, and a few miles away a young man sadly lost his life when his boat capsized. Our loss was limited to a sun awning that we had rigged to go from the boom gallows to the back stay. It blew overboard and sank. Last week in Burlington,
we saw a sale on Sunbrella fabric so we bought some. Yesterday, I spent almost the whole day with needle and thread making a new awning. The result is not nearly as neat as the professionally made one that we lost, but I think it will do the job.