Why is This Glacier Bleeding?

SCIENCE

Most glaciers weep freshwater ‘tears’—this one gushes briny ‘blood.’ (Nat Geo News)

Learn all about Blood Falls with our great resource, including educator, student, and family versions.

Teachers, scroll down for a quick list of key resources in our Teachers Toolkit.

We love the tent on the left wide of this image—it reveals Taylor Glacier’s breathtaking scale.
Photograph courtesy Peter Rejcek, National Science Foundation

Discussion Ideas

 

Illustration by Zina Deretsky / NSF

  • Where is the water in Blood Falls coming from?
    • Blood Falls is a plume rising from an ancient hydrologic system trapped beneath Taylor Glacier’s 400 meters (1,312 feet) of ice. The hydrologic system likely includes brine-saturated sediments, lakes, streams, or series of pools.

 

  • How does the liquid reach the surface of the glacier?
    • Blood Falls acts as a “pressure-release valve” for the hydrologic system.
      • The immense pressure and movement of the glacier create an “episodic artesian well” near the snout. As crevassing events create deep fissures in the glacier, liquid is forced up and out of the subglacial hydrologic system.

 

  • According to Nat Geo News, the mean temperature around Taylor Glacier is -17 degrees Celsius (1.4 degrees Fahrenheit) and little glacial melting can be seen at the surface. So how does liquid water flow from Blood Falls? Why doesn’t it freeze?
    • This is the real story. It’s not really water. It’s brine, which describes water saturated with salt. Brine has a lower freezing point than pure water.
      • The hydrologic system that feeds Blood Falls is not just saline, it’s hypersaline. Today, the water is up to three times as salty as the ocean.
      • The hypersaline hydrologic system also prevents Taylor Glacier from being frozen to the bedrock, making it unusual among Antarctic glaciers.

 

  • How did lakes and ponds form beneath 400 meters (1,312 feet) of ice?
    • About 5 million years ago, during a period called the Miocene, the ocean flooded East Antarctica, creating a salty inland lake or series of pools. Around 3 million years later, glaciers formed over the lake, trapping a basin of pristine marine 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.

 

  • Is the subglacial lake beneath Taylor Glacier really red?
    • No. The hydrologic system’s subglacial conditions exclude oxygen and light, but include large amounts of iron. The salty, iron-rich water only appears red as it interacts with the oxygen-rich surface environment at the falls, a complex chemical reaction called oxidation.
      • A similar oxidation process makes our own salty, iron-rich blood appear red when it comes into contact with (oxygen-rich) air through a nosebleed or scraped knee.

 

  • So, we know how salt got there, but how did so much iron enter the waters beneath Taylor Glacier?
    • Most of the iron comes from the continent itself. 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 hydrologic system 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 the very cold, very salty, very dark ecosystem beneath Taylor Glacier.
      • The extremophiles in the pools that feed Blood Falls are chemosynthetic, meaning they can convert sulfur and iron compounds 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.

 

  • Wrap Up: Read through our study guide on Blood Falls, and explore the discussion questions there, which are aligned to Geography Standard 7: “The physical processes that shape the patterns of Earth’s surface.” What physical processes contributed to the creation of Blood Falls? How did these physical processes shape the features of Blood Falls?
    • Flooding: The ancient ocean flooding an inland valley created the salty hydrologic system that eventually became the source of Blood Falls.
    • Glaciation: Taylor Glacier slowly covered the inland streams and pools, isolating them from most physical processes at the surface, such as climate change. Glaciation also helped introduce iron to the subglacial hydrologic system by scraping along Antarctica’s bedrock and depositing the iron-rich rubble into the lake.
    • Erosion: Chemosynthetic bacteria in the subglacial hydrologic system interact with sulfur and iron compounds to help erode the bedrock and create the lake’s unusual chemistry.
    • Oxidation: As the iron-rich water comes into contact with the air, the two substances react with each other to form iron oxide, and one byproduct is a reddish coating on the iron.

 

TEACHERS TOOLKIT

Nat Geo: What’s Really In Antarctica’s Mysterious Blood Falls

Nat Geo: Blood Falls study guide

(extra credit!) Journal of Glaciology: An englacial hydrologic system of brine within a cold glacier: Blood Falls, McMurdo Dry Valleys, Antarctica

2 responses to “Why is This Glacier Bleeding?

  1. Pingback: Top 5 places where physics laws fails - Go Physics·

  2. Pingback: This Week in Geographic History, May 8 – 14 | Nat Geo Education Blog·

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