“Alien World” (2017) A small mountain stream running through a snow cave in Mt Rainier National Park. This was one of the most interesting snow caves that I have ever found. The green/aqua colors are due to Chlamydomonas nivalis (ice algae) that grows near the surface of the snow and the blue color is the light from the sun passing through cleaner snow. I was surprised to see small plants and mosses growing in the low light environment. Snow caves generally form at high elevations in the cascade mountains after winters with heavy snowfall. Towards the end of summer, small streams form underneath the snow fields and begin to melt out snow caves from the bottom up (water is warmer than snow/ice). The snow caves are fleeting, since they continuously melt all summer and eventually disappear.