How come (Interior Alaska) rivers look so dirty?
Ever heard of “The Big Muddy?” The glacier waters of many Alaskan rivers is laden with pulverized rock. In this picture a clear stream joins a muddy glacier-fed river. The glaciers move through the mountains grinding rock and ice against the mountains and a fine dust called glacial flour (as fine as the flour in your kitchen) stays in suspension in the water, giving it that muddy appearance. The water itself is pure clean glacier water. In coastal Alaska many rivers run clearer. This is largely due to the fact that the snow melt and glacier water run over harder rocks and do not pick up as much debris. And coastal rivers come directly out of the mountains without meandering across broad valleys. Meandering rivers, sometimes called braided rivers, cover vast valleys which have more fine, loose mineral deposits from millions of years of activity, and still making its way to the sea. Most importantly, this is a natural process.
