AS A GLACIER GROWS, it scrapes up underlying rocks and soil, and carries these pieces of till with it as it travels. When the glacier melts, it can deposit these rocks in mounds called kames. If the melting glacier releases a lot of water, the pieces of rock will be carried with the water, depositing as outwash. Unlike sediments deposited in streams or lakes, the till in the Rensselaer Plateau is angular because the sediments only travel a short distance before being deposited. Because till is deposited after being transported by ice, the sediments have a wide variety of sizes as well. Till will also be less rounded than sediments deposited by streams, since constant running water will erode sediments in streams.

The southwestern area of the Poestenkill Community Forest is a glacial outwash area with deposits of sand and gravel washed out of the melting glacier approximately 14,000 to 13,000 years ago.