The acid bogs in Pownal, VT are remnants and relics of the Pleistocene. As glaciers receded in the valley between the Green Mountains on the east and the Taconics on the west 14,000 years ago, huge chucks of ice were left behind and surrounded by sediments carried by glacier melt-water. The melting of these mega-ice cubes created kettle-hole ponds which were nestled at the bottom of protective sandy ridges, establishing a cold microclimate.
Over time these ponds, cut off from nutrient-rich groundwaters, developed a sedge mat that rimmed the pond shore. Over time the sedge mat grew outward over the surface of the ponds and in turn were invaded by sphagnum moss and low, heath family shrubs. As the floating mats increased in area and thickness, they were invaded by larger shrubs and larch, black spruce, and red maple trees.
The process of bog growth and filling of the kettle-ponds is an extremely slow process. After more than ten millennia some of these bogs have completely filled in while others still have open water.