In the winter, snow falls and piles up deep. In most places, that snow melts when the spring and summer come, but in some locations, it doesn’t completely melt. The next winter, more snow falls on top of the old snow.
The cycle continues – snow falls in winter, some of it melts in the summer. Over the years, you end up with lots of layers of snow pressing down on the bottom layers – turning the bottom layers into ice.
Eventually, gravity starts its work in the ice – pulling it down the hill. The ice slowly moves downward like a giant patch of taffy stretching and pulling. Some glaciers move more rapidly, while others move very slowly – it depends on the steepness of the hill and the amount of ice that builds up.
The “toe” of the glacier is the bottom edge – and it is the place where we can measure if the glacier is growing or receding. Right now, due to global warming, most glaciers in the world are receding. That means more ice melts every summer than accumulates in the winters.
The Athabasca Glacier in Jasper National Park has receded about two kilometers (one mile) in the past hundred years. As we pedaled toward the glacier, we noticed many markers on the side of the road indicating where the toe of the glacier was in various years. If it continues to recede at this same pace, it won’t be long before there is no glacier at all!