There are a couple of lakes in Africa that do something like this — harbor pods of gas on their bottoms and then release it all at once. In that case, the gases are poison and have killed hundreds — overnight. All villages have moved away from the lakes in recent years, for good reason.
Methane pockets are not unusual. Ask anyone with a private lake for fishing or whatever. If you don’t stir the water, break up the levels within it, this shitte will happen.
They are lucky the methane didn’t come to the surface and start a forest fire. Imagine trying to explain that.
I have seen reports of an African lake that had such an erruption of methane.
They found the village with everyone and every animal dead.
That might happen with Seneca Lake.
People have homes right on the lake and the mountains rise rapidly as you move away from the water’s edge.
A large enough bubble could rapidly displace the oxygen near the surface of the lake and kill thousands in the summer when all of those summer homes are occupied.
Hobart and William Smith Colleges sit right at the Northern end. If it happened while school was in session the count of the dead could be huge.
The lakes you’re thinking of release CO2, not methane. Hugs the ground and suffocates quickly.