The greatest portion of Whitchurch–Stouffville lies on the Oak Ridges Moraine. The moraine consists of knobby hills between 290 and 373 meters above sea level of irregularly bedded layers of unconsolidated sand and gravel (built-up glacial debris) deposited by the meltwater of the Wisconsin glacier some twenty-five thousand to ten thousand years ago. In a few cases the retreating glacier left behind and buried huge blocks of ice which, when melted, created deep, water-filled depressions known as kettle lakes. Preston Lake, Van Nostrand Lake and Musselman Lake are three such examples.