Sand and other materials were deposited along the walls of these rivers. Once the ice melted, these deposits formed long, mounds of sand primarily. Eventually, water filled these craters, creating kettles. Kames are the circular mounds of outwash formed when a hole atop the glacier was filled, then deposited. As the glacier receded, huge rivers formed from the melting ice and further shifted the debris, resulting in some subtle blends of till and outwash soils.
Plant species have a remarkable ability of filling in the blanks.
Wherever some type of void exists, some type of plant will adapt to the conditions. As these soil conditions change sometimes the conditions change within a few feet the plants growing in the soil also change. In the Adirondacks, there are many types of forests. And there are many clues as to why these different forest types survive. Barring a catastrophe, such as fire or blowdown, this forest type can maintain itself indefinitely once established.