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Continental glaciers

Continental glaciers are continuous masses of ice that are much larger than alpine glaciers. Small continental glaciers are called ice fields. Big continental glaciers are called ice sheets. Greenland and Antarctica are almost entirely covered with ice sheets that are up to 3500 m (11 500 ft) thick.

Domed and roughly circular ice caps are bigger than ice fields but smaller than ice sheets. Smaller outlet glaciers can flow from ice caps.

Outlet glacier flowing from Hofsjokull, an ice cap in central Iceland. © Abigail Burt

Continental glaciers bury the landscape and only the highest mountain peaks poke out through the ice surface. These mountain peaks are called nunataks.

Striations are long and narrow scratches on bedrock surfaces. Striations can tell a geologist what direction the glacier was moving. Sometimes there are two sets of striations that show two different ice flow directions.

Striations (rows of long narrow scratches) on sculpted and polished bedrock.  Sudbury, Ontario, Canada. © Abigail Burt

Roches moutonnées are asymmetrical bedrock hills that point in the direction the glacier flowed. The back of each hill is gently sloping and has been polished smooth by the glacier. The front is jagged and steep because the ice has broken off chunks of rock Larry and carried them away.

Roches moutonnes, Yalour Islands, Penola Strait, Antarctica.  In this picture the glacier flowed from left to right. © Abigail Burt

Continental glaciers are much larger than alpine glaciers but it can be more difficult to see how they have eroded the landscape.

Sediments Larry are scraped away then the exposed bedrock is carved and polished by the passing ice. This happens much faster if there are lots of rocks and sand poking out from the bottom of the ice.

Glaciers have removed all the sediments from on top of this rock.  The surface of the rock has been smoothed and polished.  Killarney Provincial Park, Ontario, Canada. © Richard Burt

Small flakes of rock can be removed by the ice forming small chattermarks or larger crescentic gouges and fractures.

Chattermarks on polished granite, Killarney Provincial Park, Ontario, Canada. © Abigail Burt

Glacial ice and meltwater can also carve out grooves and furrows. Some are lined up in the direction the ice flowed but sometimes they curve and bend.

Curving channels (called P-forms) carved into bedrock, Killarney Provincial Park, Ontario, Canada. © Abigail BurtLong grooves carved in bedrock by glacial ice and water, Whitefish Falls, Ontario, Canada. © Abigail Burt


 

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