VOLO BOG (MCHENRY, IL)
Volo Bog began 15,000 yrs ago, when the glacier began to retreat. Large blocks of ice broke off and embedded themselves in the till or sediment left behind. The warming climate caused these chunks to melt and form kettle-hole depressions.
The kettle lake had steep banks and poor drainage. Vegetation formed a floating mat around the outer edges of the basin and slowly expanded toward the center of the lake. As decomposing plant material accumulated on the bottom, the lake began filling with vegetation.
About 375 million acres are covered by such peat bogs in glaciated regions around the world.