PHYSICAL-ENVIRONMENT OF DRUMLIN FORMATION

Review of published descriptions of drumlin fields suggests that the f ollowing conditions are important to drumlin growth: (1) compressive l ongitudinal and possibly extending transverse strain rates in the ice, (2) thin ice such as occurs near the glacier margin, and (3) high por e-water pressure in the subglacial sediments. Most drumlin fields disp lay all of these, and no fields of well-developed drumlins were found that did not. On the other hand, the lithology of drumlin-forming sedi ment appears not to be important in promoting drumlin growth, since it varied widely, nor are the lithology and large-scale topography of th e bed.