The first time I saw Lake Louise, several years ago, its beauty stunned me. Recently I visited it again, and the effect was the same: if it’s not the most beautiful spot on Earth, it’s darn close.
What created Lake Louise still hangs above it: a mighty glacier. A drive along the spine of the Rockies will show you many more of these behemoths of ice. What we don’t always appreciate is that pretty well all of Canada’s landscape was shaped by glaciers that make those that still cling to the mountains look like Popsicles.
A glacier is a huge, usually moving mass of ice. A glacier forms wherever snow falls faster than it melts for years at a time. The early snows are compressed into ice by the weight of the later snows. And eventually, when the glacier has reached sufficient depth, it will begin to move: downhill if it’s on a slope, or outward in all directions from its own weight, if it’s on a flat surface. Typically this movement isn’t every fast (a meter a day is about average), although one glacier in the ’30s was clocked at a zippy 30 metres a day.
There are four basic types of glaciers. Alpine glaciers form in high mountain valleys. When the glacier is about 30 metres deep, it begins to slowly creep down the valley, and will continue to move as long as the snowfall on its uppermost end is greater than the snowmelt, until it goes low enough that it’s melting as fast as it advances.
Piedmont glaciers are huge ice sheets formed by several alpine glaciers flowing together at the foot of a range of mountains. One in Alaska, the Malaspina Glacier, has an area of 3900 square kilometres.
That sounds pretty big, but ice cap glaciers are bigger yet; they cover most of whole islands near Norway.
But even they can’t compare to the granddaddies of all glaciers, the continental ice sheets. The glacier covering Greenland, for example, is 1.8 million square kilometres in area and 2.7 kilometres thick in spots. It’s constantly spreading out into the sea, calving icebergs, because of its own immense weight.
But even Greenland’s mighty ice sheet is small potatoes compared to Antarctica’s, which contains 91 percent of the world’s glacial ice and covers an area 1 1/2 times the size of the U.S. (minus Alaska) up to a depth of as much as 4.3 kilometres. If global warming really runs amuck, and this ice sheet melts, it will raise the sea level more than 60 metres, which would be really bad news for seaside property values.
And guess what? More than once, a similar ice sheet has covered us–most recently 10,000 years ago.
All glaciers, no matter what their type, are a lot like layer cakes. The top layer (the icing, if you like) is made up of soft, freshly fallen snow. Below that is old, granular snow, packed much more densely together. Below that is even more compacted, granular ice, called firn; and finally, at the base of the glacier is a layer of dense, clear ice that flows like a very thick fluid.
The bottom layer is under so much pressure that any cracks that form in it heal quickly, but the surface of a glacier tends to have a lot of crevasses, sometimes as much as 20 metres wide, hundreds of metres long, and 35 metres deep. Since snow sometimes completely hides these crevasses with insubstantial crusts, travelling across a glacier is a tricky business, to say the least.
Obviously, several million tonnes of ice moving across a surface is going to cause a little erosion. The rocks and other debris the glacier scrapes up as it moves are deposited in “moraines,” which form on both sides of the glacier (“lateral moraines”) and at the forward edge (“terminal moraines”). As glaciers melt, they or the debris they carry can plug valleys, resulting in spectacular glacial lakes–such as Lake Louise. (Regina was once at the bottom of an even more spectacular glacial lake, called Lake Agassiz, formed by the melting continental ice sheet at the end of the Wisconsin glaciation, which at times extended from here to the St. Lawrence. That’s why southern Saskatchewan has such rich farmland.)
The continental glaciers literally shaped this country–but as I returned to the prairies from Lake Louise, I couldn’t help but wish it had shaped it a little more spectacularly here in my backyard.
