Blood Falls is a natural—not supernatural phenomenon ! It is a liquid outflow at the snout of Taylor Glacier in East Antarctica. Many glaciers have icy outflows, but few of them are salty, and even fewer are red.

Salt Lake

Instead, Blood Falls is a plume rising from an ancient hypersaline lake trapped beneath Taylor Glacier’s 400 meters (1,312 feet) of ice. About 5 million years ago, the ocean flooded East Antarctica, creating a salty inland lake. Around 3 million years later, glaciers formed over the saline lake, trapping a basin of pristine saltwater that has been isolated for nearly 2 million years.

As water on the surface of the subglacial lake froze, the liquid below became even saltier. As liquid was removed from the lake (to form solid ice), the lake’s salt became more concentrated in the remaining water. Today, the water is about three times as salty as the ocean—salty enough that it won’t freeze, even in temperatures dipping well below the freshwater freezing point of 0° Celsius (32° Fahrenheit).

As Blood Falls gushes out of Taylor Glacier, it empties into Lake Bonney, a permanently ice-covered lake. Blood Falls’ outflow helps make Lake Bonney saline, although not nearly as salty as Blood Falls’ source lake.

Blood Falls source lake is not actually red. Its subglacial conditions exclude oxygen and light, but include large amounts of iron . The salty, iron-rich water only becomes red as it interacts with the oxygen-rich surface environment at the falls, a complex chemical reaction called oxidation

Reddish particles form as a result of a chemical reaction between iron and oxygen. The presence of salt increases the rate of this reaction, allowing the salty water at Blood Falls to appear bright red as it trickles down the glacier.

A similar oxidation process makes our own salty, iron-rich blood appear red when it comes into contact with air through a nosebleed or scraped knee.

Iron is a common substance in Antarctic bedrock —actually, it’s one of the most common elements on Earth. Scientists think iron entered Blood Falls’ subglacial lake through the scraping motion of Taylor Glacier and the activity of unusual microbe s called extremophiles. Extremophile s are able to withstand and even thrive in extremely harsh environments, including freezing and boiling temperatures. The bacteria that thrive near superheated hydrothermal vent s in the deep sea are also extremophiles.

Most autotroph s—organisms able to produce their own energy—are photosynthetic: They require sunlight and oxygen. The extremophiles of Blood Falls, however, do not use photosynthesis . They use a more unusual process called chemosynthesis . Chemosynthetic organisms are able to convert sulfur and iron compound s (not sunlight and oxygen) into energy. As Blood Falls’ chemosynthetic bacteria extract iron from the rocks they come in contact with, they gradually erode the bedrock around the lake.

Deep-Down, Outer Space

Blood Falls is a landform of interest to Arctic explorers, glaciologists, limnologist s, and microbiologists. Astrobiologist s, people who study the possibilities for life outside Earth, are also interested in Blood Falls and its unusual microbe community.

Blood Falls provides one model for how life can exist under ice in very harsh environments—no oxygen, no light, sub-zero temperatures. Many astrobiologists think that Jupiter’s moon Europa , for example, may hold a massive liquid ocean beneath its icy crust. If life exists on Europa, it may share characteristic s with the bacteria of Blood Falls.

Instructional Ideas

Read through the short, explanatory text on Blood Falls, either individually or as a class.

Have students identify unfamiliar vocabulary words or language. Review the vocabulary in the “Vocab” tab or look up words in a dictionary.

____

Discuss what physical processes are, and provide some examples.

Physical processes are natural changes that take place on or near the Earth’s surface. Physical processes lead to changes in Earth’s atmosphere, biosphere, hydrosphere, or lithosphere.



Some examples of physical processes are erosion, glaciation, sedimentation, and the effects of tectonic activity, including volcanic eruptions, earthquakes, and tsunamis.

Have students answer the two questions in the “Questions” tab.

____