Glaciers flow down through mountains on the path of least resistance. These rivers of ice are built of serene silence, howling wind and stunning beauty. Glaciers have carved mountains and plains all around the world and in the United States from the Northeast to Alaska where approximately 13 percent of the world’s glaciers still exist according to the American Geological Institute.
There are several categories of glaciers including Alpine (mountain and cirque) glaciers, Valley glaciers, Piedmont glaciers and Icefields. This article predominantly concentrates on Alpine and Valley glaciers such as are found in much of Southeast Alaska and the Northern Rockies.
Different Than an Ice Cube
Glacier ice is not simply poured and frozen. It is compacted over many years. In areas where snow falls and does not melt or evaporate during the year it carries over to the next year. Before long there could be several hundred years worth of ice crammed into a mountainous area creating an ice field where some of the compacted snow-turned-ice begins to move down hill. The grains of snow actually endure a process called firnification when they are changed into glacier ice. During this process the air spaces between the grains becomes airtight just as a handful of granola can compress when vacuum sealed in plastic.
The creeping masses of glacier ice flow with gravity and compression farther away from the ice field where the snow first fell, eventually creating a river of ice that carves its way through mountains and valleys. The glaciers push rocks out of its way and essentially bulldoze the landscape. Some glaciers are only a few miles long, where as others such as the Lambert-Fischer glacier in Antarctica reach several hundred miles in length and span a width of more than 25 miles.
A Landscape in Motion
Glaciers sculpt the land they move through, as they flow by aid of gravity and compression - pushing and carrying rock debris as they flow forward. Plowing through bedrock, the ice has a force like no other. Glaciers are what create deep fjords, flat outwash plains, deep lakes and freezing rivers. Many mountains are scraped over and have rounded summits from receding glaciers during the last little ice age. The Appalachians are a prime example of rounded mountains from when ice scraped over them thousands of years ago. Sharp pointed peaks are a giveaway to where the ice level was; if a peak is still jagged then a portion of it always remained above ice line.
Glacial melt water, often green in color is dense with silt, or glacial flour which is the pulverized rock from the bulldozing action of the ice. In coastal areas such as Southeast Alaska glacial rivers flow right out to the ocean, mixing fresh cold water with the salty seas. Some glaciers, called intertidal glaciers, end right in the ocean. These glaciers have a greater chance of calving or breaking off in thunderous columns of blue ice because of the movement of water up against them.
Global Warming
Many glaciers in this day and age are receding and contributing to a rise in sea levels worldwide. According to the Alaska Almanac, glaciers cover approximately 29,000 square miles - or 3 percent - of Alaska. Naturalist Linda Nicklin said that on average glaciers in Alaska are receding by 3 meters a year and if all of Alaska's ice melted it would cause the oceans to rise half a meter. When a glacier is receding it means that even though there is still new ice being made and it is inching forward, it cannot produce enough ice to replace the amount lost through surface melt and calving at its end. Juneau, Alaska’s Mendenhall Glacier has been receding for the last 250 years.
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