(Glacial) Rock Soup

Rocks in Alaska rock. Thanks to years of wear and tear from glaciers, many river beds (active and dry ones) contain eclectic mixes of rocks.

Here's how it works:
Glaciers are little more than ice rivers. They move extremely slowly, but they are moving. The weight of a glacier produces a lot of force that breaks and grinds rocks as the glacier advances or retreats. Since a glacier can cover an area miles long, an assortment of rocks from a large surrounding area can end up finding themselves jumbled up in the same resting place.

My favorite site for scoping pretty rocks was none other than Polychrome Glacier. On the topographic map of Denali NP, this glacier is shown as being about 1 1/2 miles long. To find it on foot, we followed the river showing signs that it was flowing from a glacial source. That is, we looked for the one with greyish water since that murkiness was the finely ground rock from glacier movement that had become mud in the river. Polychrome had receded to almost non-existence in the 15 or so years since the area had been surveyed and the map drawn up. But, it's footprint was still very clear - along the riverbed to the glacier were rocks of every color and pattern imaginable.

Really. Rocks were yellow, purple, pink, green, blue. Dull, metallic, marbled, and crystalline. Striped, polka dotted(!), swirled. From a far off distance something shined so bright on the mountain side that I thought it must be gold. Since I never got around to checking it out, I'll tell myself it was just quartz catching the sunlight just right.