Don’t worry – no real blood is running there. 5 million years ago, as sea levels rose, East Antarctica was flooded and a brine lake was formed there. After millions of years, glaciers formed on top of the lake. As they froze, the water below became even saltier. Today, the subglacial lake under Blood Falls is three times saltier than seawater and, therefore, is too salty to freeze. The water beneath Taylor Glacier, which feeds the Blood Fall, contains a lot of iron (picked up from the underlying bedrock) and when iron-rich water comes in contact with air, the iron oxidizes and takes on a red coloring, leaving blood-like stains on the ice.