Alaska Glacier Postcard

A digital rendering of an Alaskan glacier as it enters the ocean. Customizable text reading, "Alaska" also appears. A glacier is any accumulation of ice where the yearly fresh accumulation outweighs melting. Glaciers typically last for centuries or millennia. On Earth, 99% of glacial ice is contained within vast ice sheets in the polar regions, but glaciers may be found in mountain ranges of every continent except Australia, and on a few high-latitude oceanic islands. In the tropics, glaciers occur only on high mountains. Glaciers, such as that depicted here, which meet the sea are called tidewater glaciers. As the ice reaches the sea pieces break off, or calve, forming icebergs. Most tidewater glaciers calve above sea level, which often results in a tremendous splash as the iceberg strikes the water. If the water is deep, glaciers can calve underwater, causing the iceberg to suddenly leap up out of the water. The Hubbard Glacier is the longest tidewater glacier in Alaska and has a calving face over 10 km (6.2 mi) long. Yakutat Bay and Glacier Bay are both popular with cruise ship passengers because of the huge glaciers descending hundreds of feet to the water. This glacier type undergoes centuries-long cycles of advance and retreat that are much less affected by the climate changes currently causing the retreat of most other glaciers.