### Blood Falls
Antarctica — A vivid, dark-red waterfall of ancient, rusting saltwater oozes directly out of a pristine white glacier.
When geologist Griffith Taylor discovered Blood Falls in 1911, he thought the gruesome, dark-red sludge staining the pristine Taylor Glacier was caused by red algae. He was wrong. The real culprit is extreme geochemistry. Deep beneath 400 meters of ice, a hidden, hypersaline lake has been trapped in complete darkness without oxygen for 1.5 million years.
Over millennia, as the glacier's freshwater froze, the remaining liquid became an intensely salty brine, scraping massive amounts of iron from the bedrock—a process called cryoconcentration. When immense pressure forces this liquid 91 meters up through a network of fissures to the glacier's snout, the dissolved iron hits the oxygen-rich air. In a flash of chemical oxidation, it turns into ferric oxide. Essentially, the water rusts as it falls.
But how does liquid water flow through solid ice in sub-zero Antarctica? For over a century, this was a total mystery. It wasn't until 2017 that scientists using radio-echo sounding (radar) proved that the hypersaline water releases a tiny bit of latent heat when small amounts of it do freeze. This micro-heat acts as a thermal engine, warming the surrounding liquid just enough to keep Antarctica's weirdest plumbing system flowing.