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As I write this, I’ve just returned from a day trip to the Columbia Ice-fields. Needless to say, my mind is hopelessly stuck on glaciers. Before the day was over, the icefield wasn’t the only thing glacier cooled.

Glaciers are a very special type of ice. Unlike the brittle ice you find hanging from your nose while you shiver your way up the teepee town chair at Sunshine, glacial ice acts more like a very thick liquid. As ice accumulates into huge masses, there's an incredible amount of pressure on the lower layers. This pressure allows this ice to flow and begin to move very slowly under the force of gravity. The ice on the surface of the glacier isn't under pressure and so remains brittle, forming huge crevasses or cracks as it moves over obstacles.

Winter is one of the most important periods for a glacier. This is the time of year they get to actively grow and advance down the valley. Contrary to popular belief, glaciers are always moving--even during the hottest days of summer--they just sometimes melt back from the toe faster than they move forward. Think of it like a balanced budget. If the glacier moves forward about 18 metres in a year, but melts backward 23 metres during the summer, than the net movement is 5 metres up the valley. We call this a receding glacier and this is the situation on most glaciers in Alberta today. The above example describes the Athabasca Glacier on the Columbia Icefields.

Glaciers deserve a lot of the credit for the many roads and trails through the Rockies. Prior to the last ice age, most of the valleys had been carved by the action of streams, leaving a very deep and sharp V-shaped valley. These would have been very difficult to build roads in. As the glaciers came onto the scene, they inherited many of the same drainage patterns developed by the rivers and slowly sculpted them into nice wide U-shaped valleys. This would make later exploration and development in this area much easier (although some of the old-timers that built the Banff/Jasper and other highways in the area would dispute that fact).

Glaciers, of themselves, actually do very little eroding. Ice doesn't have the ability to erode, but if you think of a glacier as just a very slow moving river of ice, you begin to get a clearer picture. It's the material carried within the river that acts as an abrasive and carves away at the valley. Glaciers pick up rocks and debris along their margins and this material is carried as it moves down the valley. These rocks form a powerful abrasive and slowly scrape and scour the valley bottom. As you might imagine, these rocks are quickly ground into a fine powder known as rock flour which then makes its way into our streams and lakes giving them the incredible colours known the world over.

Although we usually think of glaciers during the summer when they seem more visible, they are truly a year round phenomenon and worth studying at any time of the year.