Blood-red water in the mountains of Peru

The embedded image is a screencap from a title gif at The New York Times.

For thousands of years, the glaciers were replenished with ice in the winter. But they have shrunk by more than 40 percent since 1968, uncovering rocks that, when exposed to the elements, can trigger chemical reactions that leach toxic metals into the water and turn it acidic...

Deglaciation above Lake Shallap, the headwaters of Shallap River, has exposed more than 380 acres of the Chicama Formation, which is rich in pyrite, an iron sulfide. As meltwater trickles across the rocks, the pyrite transforms into iron hydroxide and sulfuric acid, a corrosive chemical that releases heavy metals from the rock into the meltwater, Dr. Loayza said.

Pure water has a neutral pH of 7; Lake Shallap now has a pH of less than 4, nearly as acidic as vinegar. It also contains lead, manganese, iron and zinc at levels that surpass environmental quality standards...

This process is causing major problems for fish, wildlife, vegetation, and humans living downhill from the drainage.  I wonder if similar events occurred during the centuries of Inca rule of this region.  The image of what appears to be blood cascading down from some mountain sites might have had a profound effect of native theology.

The source link has a long discussion of the situation and lots of photos.