Believe it or not many people do not know what a glacier is or that there are different types of glaciers.
What is a Glacier
First off, a glacier is created when snow piles up. Snow is made from ice crystals and depending on the conditions snowflakes can be fluffy with lots of empty space. As snow sits it settles. As more snow falls on top of it, it compresses. As the snow continually gets compressed the space disappears and over time it becomes a solid piece of ice. In relation to glaciers, very large sheets of ice.
Because of their enormous mass gravity does an excellent job at pulling glaciers down. Ice has a certain level of plasticity, meaning it can be molded like clay, it just takes a lot more pressure and patience. Over time ice that was snow on the top of the mountains forms into glacier ice and then eventually flows to the front of the glacier. In most cases with longer Alaskan Glaciers it's a matter of thousands of years.
Types of Glaciers
In Alaska there are eight types of glacier formations. They are; ice fields, mountain glaciers, valley glaciers, tidewater glaciers, piedmont glaciers, hanging glaciers, cirque glaciers, and ice aprons. Other glacier related formations are rock glaciers, ice shelves, ice caps, ice streams, and ice sheets.
Icefields are like the hub of wheel with glacier spokes. They are places where snow gets deposited across a very large area usually sending glaciers out in different directions. A popular icefield is Harding Icefield, accessed along Exit Glacier near Seward.
Also called alpine glaciers, mountain glaciers start high in the mountains and flow through mountainous areas generally lined with peaks on both sides.
Valley glacier are typically mountain glaciers that travel long distances across a fairly level valley before reaching it's terminus. The most popular valley glacier in Alaska would be Matanuska Glacier, near Glacier View off the Glenn Highway. Another popular valley glacier is Valdez Glacier in Valdez. It terminates in a lake creating icebergs.
Tidewater glaciers are valley glaciers that make their way to salt water. They are spectacular to watch calve as often their terminus consist of a large steep face. Popular tidewater glaciers in Alaska include Columbia Glacier near Valdez, Taku Glacier near Juneau, and many of the glaciers in Glacier Bay National Park.
Hanging glaciers are often the result of the retreating of a mountain or valley glacier whos terminus now hangs against the side of a cliff or steep mountain side. Popular hanging glaciers in Alaska include Rainbow Glacier in Haines, Twentyseven Mile Glacier just outside Valdez at 27 mile on the Richardson Highway.
Cirque glaciers are bowl like glaciers usually wider than they are long as such they are usually not named.
Ice aprons are small glaciers that cling to the steep sides of high mountains. Most ice aprons in Alaska are not named cause they are so small compared to the many larger glaciers.