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.
Blood Falls is not the melted residue of Taylor Glacier, which is a typical continental glacier, descending from a plateau on the Antarctic Ice Sheet about 54 kilometers (35 miles) away.
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 microbes called extremophiles. Extremophiles are able to withstand and even thrive in extremely harsh environments, including freezing and boiling temperatures. The bacteria that thrive near superheated hydrothermal vents in the deep sea are also extremophiles.
Most autotrophs—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 compounds (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, limnologists, and microbiologists. Astrobiologists, 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 characteristics with the bacteria of Blood Falls.
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.
Have students express the ideas of the text in their own words. Re-write the text, draw a diagram or series of illustrative/cartoon panels, create an animated video, etc. As an example, read and download a diagram of Blood Falls and its unusual microbial communities here.
Antarctic Ice Sheet
thick glacier covering most of Antarctica.
person who studies the possibility of life in outer space.
organism that can produce its own food and nutrients from chemicals in the atmosphere, usually through photosynthesis or chemosynthesis.
(singular: bacterium) single-celled organisms found in every ecosystem on Earth.
a dip or depression in the surface of the land or ocean floor.
solid rock beneath the Earth's soil and sand.
particular feature of an organism.
process that involves a change in atoms, ions, or molecules of the substances (reagents) involved.
process by which some microbes turn carbon dioxide and water into carbohydrates using energy obtained from inorganic chemical reactions.
substance having at least two chemical elements held together with chemical bonds.
items gathered closely together in one place.
ice sheet that covers an enormous area.
to go from a higher to a lower place.
conditions that surround and influence an organism or community.
to wear away.
moon of Jupiter.
to purposely leave out.
to pull out.
microbe that is adapted to survive in very harsh environments, such as freezing or boiling water.
narrow opening or crack.
mass of ice that moves slowly over land.
study of glaciers and ice sheets.
opening on the seafloor that emits hot, mineral-rich solutions.
type of lake with a very high salt content.
chemical element with the symbol Fe.
to set one thing or organism apart from others.
a prominent feature that guides in navigation or marks a site.
the geographic features of a region.
person who studies lakes and ponds.
tiny organism, usually a bacterium.
study of the structure, function, and behavior of microscopic organisms.
natural satellite of a planet.
water, sediment, and chemicals discharged by a river or other flowing body of water.
chemical process of a substance combining with oxygen to change the substance's physical and molecular structure.
chemical element with the symbol O, whose gas form is 21% of the Earth's atmosphere.
to penetrate or pass through every part of something.
an unusual act or occurrence.
process by which plants turn water, sunlight, and carbon dioxide into water, oxygen, and simple sugars.
large region that is higher than the surrounding area and relatively flat.
single, upward flow of a fluid, such as water or smoke.
pure or unpolluted.
material left over after something has been removed.
to dissolve and form a brittle coating, as iron does when exposed to air and moisture.
end of a glacier.
inland body of fresh water that exists under a glacier or ice cap.
having to do with powers not explained by science or nature.