Either a underground river or a methane pocket. Sites lak is a "blue hole" that has a underground river under it. In 1846 a guy dug a ditch from it to make his farm land bigger. Well it caused the shore line to fall in turning it into a 60 acre lake. They felt it up to 16 miles away, the people at the time thought the world was ending. There's another story of a diver getting sucked into a underground river near baileys lake and ending up popping out in Charles mills or sites lake, been a minute since I've heard the story. Also that area is full of gas wells, so could be gas if its been steady for years.