HOW A GLACIER IS FORMED
The three main ingredients in the formation of a glacier are time, snow, and cool summers. The Gulf of Alaska sends lots of moisture to Southcentral Alaska, giving the Harding Icefield an average of 60 feet of snowfall every winter. Glacial ice forms relatively quickly in Alaska, in just four to ten years. When snow first falls, it is about 80% air. As time passes and that snow receives additional snowfall on top of it, more and more air is compressed out. Once the snow has compacted to a point where it is only 50% air it is called firn, part of a process called firnification. Given more time and more snowfall, the snowpack will reduce to 20% air, and at that point it has become glacial ice.
WHY IS THE ICE BLUE?
One of the most common questions about glaciers that we get on our cruises is: why is the ice blue? White light includes a spectrum of different wavelengths that are represented by all colors of the rainbow. When light hits denser ice, the denser ice absorbs all colors of the wavelengths except the shorter, high-energy blue wavelength. The blue wavelength is reflected back, making the ice appear blue.