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Sirmilik National Park of Canada

Geology

Sirmilik is an Inuktitut word meaning “the place of the glaciers”. Much of the park is covered by high mountain peaks and glaciers, although there are extensive plains of low-lying tundra as well. The Byam Martin mountains on Bylot Island are part of the larger Arctic Cordillera which extends from the eastern flank of Baffin Island all the way up to Ellesmere Island. Many interesting geological features are found within the park.

Glacial features

Glaciers, mountains and cirques, Bylot Island © Canadian Wildlife Service

The area has been scoured by both continental ice (the Laurentide Ice Sheet of the Wisconsin glaciation, which began its retreat from the area around 6000 - 8000 years ago), and localized alpine or cirque glaciers. Cirque glaciers have influenced the mountainous areas of the park, carving out sharp peaks, ridges, and valleys. Mountain peaks called nunatuks protrude from the icefield regions of the park.

Glacial features that can be seen in the park include:

  • Icebergs – formed when large chunks of ice break off from glaciers. These spectacular sculptures of floating ice can be seen in the marine waters year-round, and are common between Pond Inlet and Bylot Island. Sometimes they are brought in by ocean currents from as far away as Greenland, or Devon Island.
  • Moraines – ridges or mounds formed by rock debris that were transported by moving ice and deposited at the margins of glaciers. End moraines show the farthest point of a glacier's advance, while lateral moraines show the location of the glacier's sides.
  • Cirques - bowl-like hollows carved out by glaciers in the tops of mountains. Some cirques are ice-free, while others are still occupied by glaciers. Many of the park's sharp mountain peaks and ridges were carved by cirque glaciers.
  • Sand Deposits – created by the erosive actions of ice, wind, and water. Sand and other fine particles are carried by the wind from moraines and outwash deposits.
  • Talus or Scree Slopes – cone-shaped accumulations of rocks pried loose from steep glacier-scoured valley walls by frost action. Active talus slopes are unstable and could be dangerous to hikers. Rock surfaces that are lichen-free provide clues that the slope is still active and prone to fresh rockfall.

Hoodoos

Hoodoos © Lee Narraway

The hoodoos of the Borden Peninsula area are a fascinating feature in the park. The tall towers and spires of red-tinged sandstone and sedimentary bedrock have been sculpted by centuries of erosion by wind and water. The hoodoos are found at several locations, generally within 2 – 3 days travel on foot from Navy Board Inlet.

Tundra Polygons and Pingos

These interesting landforms are formed by the freeze-thaw actions of water and ice within the permafrost. Permafrost is frozen rock or soil. It always remains below 0°C, except for the surface layer that thaws during the summer. In the arctic, permafrost is continuous.

The interesting shapes of the tundra polygons are formed by ice in the permafrost of the tundra, combined with patterns of melting at the surface. The water-retaining capacity of these topographical features, combined with poor drainage of the underlying permafrost, has contributed to the formation of these wetland features.

Tundra Polygon © Christian Kimber

Pingos are formed when underground water pockets create pressure on the frozen ice above, lifting the overlying frozen sediment. Pingo ice is formed by the freezing of the injected water. The repetition of this process over time leads to the formation of an underground ice core of several cubic metres, which heaves the tundra upwards forming the pingo. Lake drainage can create the conditions necessary for the formation of pingos.