On a hike last month in the San Juans, I came upon a little side creek flowing into Bear Creek that startled me and got my curiosity up so much that I took some pix and even asked the two college-aged girls having lunch nearby if they knew what was up (having learned that on many a trail, those who are half my age often know twice as much.) They, too, were mystified.

The two creeks met near the Yellow Jacket Mine, the turn-around point of my hike. Bear Creek above the fork was clear as a bell:



But where they joined, the smaller creek, labeled South Fork (of Bear Creek) on my map that came down from Engineer Pass, had the riverstones covered in a white film or crust:



At the pool where they met, the water had a milky quality to it that reminded me of the glacial or rock flour creeks seen in the high streams in the Canadian Rockies. I'd never really seen anything like it before in Colorado; the streams I've seen here are all pretty much crystal clear. The area was littered with mines, but this wasn't the red-tainted tailings water I had seen up by Ironton and Red Mountain Pass.

The milky quality went away less than a hundred yards from the meeting point of the two creeks.

Any ideas on what causes this:



(I'm hoping that the answer's not so simple someone's 5th-grader responds or I'll be taking advice from someone 1/5 my age.)
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I've seen something similar before - creeks often get cloudy with minerals that leach into the water from the dirt and rocks they're flowing through. Opal Creek in Big Basin (a California state park) is named for it; the minerals in the water give it opal-esque coloration.

After seeing the film Gasland, I'm hoping fracking has nothing to do with it.


http://www.ewg.org/reports/injection

http://www.pbs.org/now/shows/613/index.html

Perhaps the cloudy part and white rocks represent higher water levels when the water from the creek that Bear Creek flows into encroaches into Bear Creek. If each creek had vastly different chemical characteristics minerals could leach out where the two waters meet. This would happen with different pH values. Water in mining areas are often very low pH yet have lots of dissolved minerals, that would leach out if hit with higher pH water. When I worked in coal mines, the water in the bottom of the pits had a pH of 4.0 yet TDS well over 5,000.