Employees at the Damariscotta Lake Watershed Association have reported feeling tremors strong enough to rattle the windows of their office on Damariscotta Lake in Jefferson on three separate mornings recently.
“We haven’t experienced anything like it here before,” said Nancy Holmes with the DLWA.
Two of the DLWA’s neighbors, one on each side, have also felt tremors, said Julia Davis, DLWA Stewardship Coordinator. “One of the neighbors is set back a bit from the lake, too.”
According to National Weather Service data, there was no seismic activity in the area at those times, so it was not an earthquake, said Kim Kaiser, Deputy Director of the Lincoln County Emergency Management Agency.
At first, county EMA officials speculated that residents may have been feeling the results of blasting at the construction site for the new Jefferson Village School building.
However, JVS was in session at the times the tremors were felt, and school officials said no blasting occurred at that time, nor would it ever be permitted to occur so close to the school while children were present.
At this time, it appears that the tremors were caused by shifting ice on Damariscotta Lake, said Jefferson Road Commissioner Alan Johnston who was brought in to inspect the DLWA office and consult on the issue.
The tremors were caused by two large pieces of ice pushing into each other as the lake freezes, causing a “pressure ridge,” Johnston said.
As the massive pieces of ice push into each other, the force of cracking ice and the sheets sliding against each other create vibrations that result in the tremors felt along the shore.
“That’s my explanation,” Johnston said. “I don’t know if it’s right or wrong.”
The tremors caused by the pressure ridge are very similar to the way earthquakes are created. In an earthquake, massive pieces of the earth’s crust called tectonic plates slide into each other – just like the ice sheets on the lake creating a pressure ridge.
When friction builds between tectonic plates, it can cause sudden slippages and splits, and the resulting vibrations are earthquakes.
Although the pressure ridge explanation fits the circumstances surrounding the Jefferson tremors, the pressure ridge itself is hard to explain, Johnston said.
Normally pressure ridges only form in the narrowest parts of the lake, Johnston said. For some reason, this ridge extends far out into an open part of the lake.
“I’ve never seen it go out into the bay the way it is this year,” said Johnston, who has lived all of his 51 years in Jefferson.
