The withdrawal of a glacier create a vast wetland which will gradually be tamed by men who will make ponds.
Erratic block of stone
called "Pierre Mourey", in les Fessey
After the glacier
Over the last two million years of the Quaternary period, a thick blanket of ice covered the plateau. This ice sheet disappeared about 12,000 years.
Ponds, like other wetlands (swamps or bogs) nest mostly in depressions formed by glacial erosion.
The monks were the first masters of water management. They created ponds.