A kettle lake, kettle pond, kettle hole or pothole is a depression or hole in an outwash plain formed by retreating glaciers or draining floodwaters. The kettles are formed as a result of blocks of dead ice left behind by retreating glaciers, which become surrounded by sediment deposited by meltwater streams as there is increased friction. The ice becomes buried in the sediment and when the ice melts, a depression is left called a kettle hole, creating a dimpled appearance on the outwash plain.
Lakes often fill these kettles; these are called kettle hole lakes. Another source is the sudden drainage of an ice-dammed lake. When the block melts, the hole it leaves behind is a kettle. As the ice melts, ramparts can form around the edge of the kettle hole. The lakes that fill these holes are seldom more than 10 m (33 ft) deep and eventually fill with sediment. In acid conditions, a kettle bog may form but in alkaline conditions, it will be kettle peatland. Kettle lakes are found in all glacial areas.
I read some of the article (the formatting was difficult). I guess what makes this “bottomless” lake (78’ deep!) special somehow is that the bottom sediments are “fed” a constant stream of air from the porous limestone below it. (Not sure how that works.) They said it was beneficial to keep the sediment layers from decaying. But then I would think that the air would bring modern-day contaminants into the sediments?
The article was just a fluff piece with no science behind it. I imagine that they take samples and have all sorts of data regarding pesticides, heavy metals, etc. Of course an ash layer 30 feet deep and 6000 years ago (or whatever) would indicate a large volcanic eruption which resulted in more “climate change” than we’ll ever do.
Or - even 200 years ago. 1815, “The Year without Summer” due to the eruption of Mount Tambora in Indonesia.