There is a corner of Antarctica that looks like something out of a David Cronenberg movie. It’s located in the dry valleys of McMurdo, an immense frozen desert where, periodically, a jet of crimson liquid suddenly gushes from the dazzling white of the Taylor Glacier. They’re called the Blood Falls, and since their discovery in 1911 by geologist Thomas Griffith Taylor, they’ve fueled a century of scientific speculation.

Recently, a series of observations conducted since 2018 have clarified several mysteries, such as the nature of their reddish color and what keeps them liquid at almost –20 degrees Celsius. New research published this week in the journal Antarctic Science adds the final piece to the puzzle, clarifying what phenomena drive the falls to gush from underground.

The Science Behind the Blood Falls

At the time of their discovery, Taylor attributed the color to the presence of red microalgae. More than a century later, scientists have determined that the red is due to iron particles trapped in nanospheres along with other elements such as silicon, calcium, aluminum, and sodium. These were likely produced by ancient bacteria trapped underground in the area: Once in contact with air, the iron oxidizes, giving the mixture its characteristic rust color.

As for the presence of liquid water, it is actually a hypersaline brine, formed about 2 million years ago when the waters of the Antarctic Ocean receded from the valleys. The very high salinity of this brine prevents the water from freezing, thus allowing it to gush out periodically.

The New Discovery

With the temperature puzzle solved, the question remained as to what physically drove the fluid to erupt. The answer came from cross-referencing GPS data, thermal sensors, and high-resolution images collected in 2018 during an eruption. The analysis demonstrated that the Blood Falls are the result of pressure variations affecting the brine deposits beneath the glacier.

As Taylor Glacier slides downstream, the overlying ice mass compresses the subglacial channels, building up tremendous pressure. When the strain becomes unbearable, the ice gives way: Pressurized brine seeps into the crevices and is shot out in short bursts. Curiously, this release acts as a hydraulic brake, temporarily slowing the glacier’s march. With this discovery, the mysteries of the Blood Falls should finally have been solved, at least for now. The impact of global warming on this complex system in the coming decades remains unknown.

This story originally appeared on WIRED Italia and has been translated from Italian.