The low ridge winding across the landscape of the Arrow Hills, Manitoba, Canada, is a classic esker. When a great ice sheet covered central North America, more than 10,000 years ago, a stream of meltwater ran beneath it at this location. The abundant sand and gravel, fresh-made under the glacier's belly, piled up on the streambed while the stream melted its way upward. The result was an esker: a ridge of sediment in the form of a rivercourse.
Normally this kind of landform would be wiped out as the ice sheet shifts and the meltwater streams change course. This particular esker must have been laid down just before the ice sheet stopped moving and began to melt for the last time. The roadcut reveals the stream-laid bedding of the sediments composing the esker.
Eskers can be important pathways and habitats in the marshy lands of Canada, New England and the northern Midwestern states. They are also handy sources of sand and gravel, and eskers can be threatened by aggregate producers.
