The climax of Wisconsin glaciation occurred approximately twenty thousand years ago. At that time ice sheets covered all of the up-state New York and extended Southward as far down as New York City. Except for the terminal moraine, all other morainal deposits in New York State are recessional, indicating periods of stagnation as the ice retreated across the state toward the North. Morainal topography everywhere in the state seems to be very pitted. This is due to the presence of kettle holes.
Kettles occur when blocks of ice are isolated from the receding glacier terminus.
These blocks of ice are then partially or totally covered by moraine, lake or outwash plain sediments. When these blocks of ice melt, the sediment overlying them collapses and the melted ice leaves in its place surface depressions, or kettle holes. These lakes are usually small, have a rounded outline, and have poorly integrated feeder and outlet streams. Both kettle ponds and kettle holes can be observed in Mendon Ponds Park. Morainal areas in the region often contain kames.