It currently retreats at 25-27 feet per year. When the flow exceeds the melt the glacier advances. As the glacier moves down the valley it grinds the underlying surface and rocks, soil, silt etc are taken down the valley to where the glacier terminates. The glacier deposits it's load into landforms called moraines. The silt deposited in the lake turns it a milky blue colour.
Blue ice is one of the most interesting and spectacular features of the glacier.
The crystaline structure absorbs and reflects the light. As light strikes the surface, all colours of the spectrurm are absorbed except blue, which is reflected back. The area around the visitor centre is green and lush. A small green beaver pond, complete with dam, sits beside one of the viewing centres. The white head of an eagle is spotted on the top of a tree.