The park protects the Southern Boreal Plains and Plateaus Natural Region - a transitional zone between the aspen parkland to the south and the boreal forest to the north. Elk Island National Park is knob and kettle topography rising thirty to sixty metres above the surrounding plains of Alberta. Elk Island National Park is an island, not in the geographical sense, but in terms of its landscape of small hills and depressions surrounded by flat plains. When the glaciers retreated from the area, they left debris clustered around chunks of ice that formed the knobs, while the melting ice made shallow ponds or kettles. These are eutrophic ponds, meaning they have a very poor oxygen supply, but they contain rich accumulations of nutrients, making them an excellent habitat for plants and wildfowl. The park has more than 250 lakes, ponds and wetlands over 20% of its surface area. Astotin Lake, near the park’s north end is 3.9 kilometers long, almost 3.1 kilometers wide and .5 - 10 meters deep, the parks largest body of water.