The Margerie Glacier in Alaska’s Glacier Bay National Park is 21 miles long and 250 feet high (with a base 100 feet below sea level). Seeing this tidewater glacier’s clean, blue face is a highlight for visitors.
There’s something about the blue color of glacier ice that leaves a lasting impression. It may be because glacier-blue is a hue that can’t be duplicated anywhere else or by any other means. I find it the most beautiful blue in all of nature.
How is this entrancing and unique color created? Scientists tell us that the glacier-blue color arises due to some surprising interactions between light and water molecules.
Snow looks white, although a single snowflake viewed up close is actually clear. When snow piles up, it’s mostly air. And when light hits those air pockets, the faces of ice crystals act like bazillions of tiny mirrors, scattering the full spectrum of white light in every direction.
Glaciers form when more snow falls than melts over a period of years, compacts into ice and then becomes thick enough to begin to move. As the ice becomes thicker, the weight of it squeezes out the air bubbles between the crystals. In other words, a snow patch becomes a glacier when the deepest layers begin to deform due to the weight of the overlying snow and ice.
Even within ice, water molecules are able to vibrate. But they only vibrate at certain, special frequencies. Light is made up of wavelengths, and each wavelength is a particular color. The color we see is a result of which wavelengths are reflected back to our eyes. As white light passes through the glacier ice, red and orange frequencies (or long wavelengths) are just right to be absorbed by the water molecules, and they start vibrating. The blue (or short wavelength) light is what gets transmitted and scattered. So, white light minus red-orange, absorbed light leaves us with the brilliant blue of glacier ice.
Air bubbles are squeezed out of glacier ice, so white light isn’t scattered. The ice absorbs the red part of white light, and the blue light is what gets transmitted to our eyes.
The red-orange light, however, isn’t absorbed very strongly, so it takes many, many feet of ice to give us the stunning, glacier-blue color.
Sadly, that beautiful blue hue is disappearing from our world as most of our glaciers melt and retreat. Watch the video below, filmed at Mendenhall Glacier in Tongass National Forest in Alaska. It explains not only how the glacier-blue color is created but also points out that it might be the only example on Earth where color comes from vibrations.
We live on a blue dot of a planet. The blue color we see when we stand in the presence of glaciers reminds us of that truth.
Here’s to finding your true places and natural habitats,
Candy
Beautiful. I’m still not convinced glaciers are blue for a “completely different reason” than the sky is, but it is worth taking in regardless.