In broad strokes, the story of glaciers in Vermont goes something like this: Earth entered our most recent glacial period – the Quaternary Glaciation – about 2.6 million years ago. The most recent glaciation, known as the Ice Age (there are 12 glacial periods during the Quaternary Glaciation) began about 110,000 years ago as the climate cooled again. Year after year the glaciers advanced, on the east coast extending as far south to Long Island and down just south of to the northern border of the US out west. They reached their maximum extent 25,000 years ago, at which point the climate changed (the Barents Sea near Norway/Russia burped up some epic methane burps – article) and the glaciers began to retreat. As they retreated, the melt water formed large bodies of fresh water throughout the state, including Glacial Lake Vermont (13,500-12,000 years ago), which filled the Champlain Basin to about 620′ in elevation. Eventually, the Laurentide ice sheet had retreated far enough north exposing the basin to the St Lawrence seaway, allowing the fresh water to drain out (in a matter of hours) and salt water to slowly flow in, mixing in with the remaining water, giving rise to the Champlain Sea was born. The Sea filled the basin to about 320′ with salt water, but by about 10,000 years ago the Sea had reverted to a fresh water body of water, what we know and love as Lake Champlain (more on this later).