Twenty-nine kettle lakes, one of the largest eskers in Ontario, sand dunes, and other post-glacial formations are strewn about this park, left behind by a retreating glacier some 10,000 years ago. An esker is a narrow, winding ridge of gravel or sand, deposited by the melting waters under a glacier. Munroe Esker runs some 249 kilometres in a north-south direction.

The park sits atop a continental divide known as the Arctic Watershed. Rain on the south side flows to the Atlantic; rain on the north side flows to James Bay.
The thick, boreal forest is not as varied as similar forests elsewhere, due to a fire that ravaged the area in the early 1950s. The intense heat activated many seed-bearing pine cones to open, and today, the jack pine trees that resulted are all the same age and height. The woods shelter moose, fox, black bear, wolf, lynx, beaver, mink and muskrat. Loons, great blue herons, ruffed grouse, owls, and warblers are among the birdlife present.