According to Bennet And Glasser (1996), drumlins are typically smooth, oval shaped or elliptical hills composed of glacial sediment. There are between 5 and 50 meters high and 10-3000 m long. The steep, blunter end usually points in the up-ice direction. Drumlins are composed of a variety of materials including: (1) lodgement till, (2) bedrock, (3) deformed mixtures of till, sand and gravel, and (4) undeformed beds of sand and gravel.
Drumlins are not uniformly distributed under the glacier and form in distinct fields which are sometimes called to as drumlin swarms. Bennet and Glasser (1996) cite Chorley (1959) who examined the shape of drumlins. He notes that drumlins have a shape similar to the cross section of hydrofoils or aircraft wings. He argues that the elongated drumlins formed under fast flowing ice because it is analogous to air plane wings which can withstand higher air speeds because of their elongated shape. He also notes that drumlins formed under slow moving ice should be more rounded than those under fast moving ice due to extended pressure.
The drumlins of western and central New York comprise the largest group in the world. The New York field includes a variety of form, attitude, and relationship that exemplifies the diversity of this glacial feature. The Ontario drumlin field is a belt about 35 miles bordering the south side of Lake Ontario and extends for about 140 miles from Syracuse to the Niagara River (Cashman, 1986). Figure # is an example of the Palmyra Quadrangle which is an example of a drumlin field.
The greatest development of the New York drumlins was in conjunction with the following favourable conditions: (1) character of the strata providing an abundance of pasty till; (2) topography of the Ontario Basin and lowland; (3) the movement of the glacier controlled by the land features; and (4) thrust movement of the ground-contact ice. We should note that the drumlin area of western and central New York was formed from 279-290 feet lower during the glacial period than it is today. This field includes over 10,000 drumlin crests (Cashman, 1986).
Return to The Geology Club page