Glacier viewers are sometimes surprised to see the different colors a glacier such as Marjerie glacier can present. Glacial colors go far past mere white.
The white part of a glacier is snow fall that is relatively new. It usually appears jagged, uneven, and even worn, due to exposure to the surrounding elements. This white snow also contains a large amount of air bubbles inside the snow crystals. These snow crystals actually freeze to the glacier ice, slightly enlarging and smoothing the crystals.
As more snow falls, it adds weight to the snow crystals already frozen to the glacier ice. Over time, the compression from this added weight forces the air bubbles out of the snow and ice crystals. The result is almost pure ice. The blue color of the light spectrum can not be readily absorbed by the pure ice and reflects the blue color to meet our eyes. The older the “pure ice”, the deeper the blue can appear. This process can take thousands of years.
As a glacier slowly moves down its path, it is constantly moving parts of the earth under it and beside it. The parts of earth being moved are called moraine or glacial till. These pieces can be very small, like dirt or gravel, to very large rocks and even boulders. This glacial till usually appears brown, gray, or black, depending on the composition of earth being moved. Glacial till can actually be found on top of certain parts of a glacier, down in the crevices of a glacier, or maybe look like stripes or layers in the face of the glacier.
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Based on the above text and your observations at Marjerie Glacier, please answer the questions below as best you can.
1- Is blue ice visible?
2- Describe where you see blue ice. (On it’s face, top, bottom, in crevices, in a hole, etc)
3- What causes the ice to appear blue?
4- Will the white areas you see be able to appear blue in our lifetime? If not, why?
5- Do you see any brown or black colors on the glacier?
6- Please describe where you see browns or blacks. Do you see anything that looks like brown or black layers on the face?
7- What is the cause of the browns and blacks?
Resources;
www.NPS.gov//common questions and myths about
glaciers
http://www.fromthelabbench.com/from-the-lab-bench-science-blog/when-glaciers-get-dirty-attack-of-the-cryoconites
https://en.m.wikipedia.org/wiki/Margerie_Glacier
https://en.m.wikipedia.org/wiki/Glacier_Bay_Basin