McMurdo Dry Valleys

Coordinates: 77°28′S 162°31′E / 77.467°S 162.517°E / -77.467; 162.517

"Dry Valleys" redirects here. For other uses, see dry valley

Map of the McMurdo Sound and the Dry Valleys

Location of valleys (indicated by red dot) within the Ross Dependency

The McMurdo Dry Valleys are a row of snow-free valleys in Antarctica located within Victoria Land west of McMurdo Sound.^[1] The region is one of the world's most extreme deserts, and includes many interesting features including Lake Vida and the Onyx River, Antarctica's longest river.

Climate

McMurdo Dry Valleys, Landsat 7 imagery acquired on December 18, 1999.

The Dry Valleys are so named because of their extremely low humidity and their lack of snow or ice cover. They are also dry because, in this location, the mountains are sufficiently high that they block seaward flowing ice from the East Antarctic ice sheet from reaching the Ross Sea. At 4,800 square kilometres (1,900 sq mi), the valleys constitute around 0.03% of the continent, and form the largest ice-free region in Antarctica. The valley floors are covered with loose gravel, in which ice wedge polygonal patterned ground may be observed.^[2]

The unique conditions in the Dry Valleys are caused, in part, by katabatic winds; these occur when cold, dense air is pulled downhill by the force of gravity. The winds can reach speeds of 320 kilometres per hour (200 mph), heating as they descend, and evaporating all water, ice and snow.^[3]

Geology

ASTER image of the Dry Valleys.

The valleys cut through the Beacon sandstone, as well as older granites and gneisses of the Ross Orogeny. Tills, deposited directly from ice, dot this bedrock landscape. These tills are relatively thin and patchy, and differ markedly from the extensive, mud-rich tills of the Laurentide ice sheet in the Northern Hemisphere. One reason for the difference is that most of the tills in the Dry Valleys were deposited from cold-based ice (ice with basal temperatures below 0 °C (32 °F)), whereas the Laurentide ice sheet was largely wet-based, with significant melting at the base and at the glacier surface.

Biota

Unusual bacteria have been found in Blood Falls at the tongue of the Taylor Glacier, above the ice-covered surface of Lake Bonney in Taylor Valley.

Mummified seal carcass

Endolithic photosynthetic bacteria have been found living in the Dry Valleys, sheltered from the dry air in the relatively moist interior of rocks. Summer meltwater from the glaciers provides the primary source of soil nutrients. Scientists consider the Dry Valleys perhaps the closest of any terrestrial environment to the planet Mars, and thus an important source of insights into possible extraterrestrial life.

Anaerobic bacteria whose metabolism is based on iron and sulfur live in sub-freezing temperatures under the Taylor Glacier, staining red the ice emerging at Blood Falls.^[4][5]

Part of the Valleys was designated an environmentally protected area in 2004.

Major geographic features

Valleys

• Alatna Valley (sometimes incorrectly spelled Atlanta Valley^[6]) is the northernmost, north of Benson Glacier.

From north to south, the three main valleys are

• Victoria Valley (between St. Johns Range in the north and Olympus Range in the south)
• Wright Valley (between Olympus Range in the north and Asgard Range in the south)
• Taylor Valley (between Asgard Range in the north and Kukri Hills in the south)

West of Victoria Valley are, from north to south,

• Barwick Valley
• Balham Valley
• McKelvey Valley

Stretching south from Balham Valley are, from west to east:

• Priscu Valley
• Wall Valley
• Virginia Valley
• Stuiver Valley

West of Taylor Valley is

• Pearse Valley (sometimes incorrectly spelled Pearce Valley).

Further south, between Royal Society Range in the west and the west coast of McMurdo Sound at the lobe of Koettlitz Glacier are, from north to south:

• Garwood Valley
• Marshall Valley
• Miers Valley

Lakes

Some of the lakes of the Dry Valleys rank among the world's most saline lakes, with a higher salinity than Lake Assal (Djibouti) or the Dead Sea. The most saline of all is small Don Juan Pond.

• Lake Vida (Victoria Valley)

• Lake Vanda (Wright Valley)
• Lake Brownworth (Wright Valley) (freshwater)
• Don Juan Pond (Wright Valley)

• Lake Fryxell (Taylor Valley)
• Lake Hoare (Taylor Valley)
• Lake Chad (Taylor Valley)
• Dirty Little Hoare Pond (Taylor Valley)
• Parera Pond (Taylor Valley) (freshwater)
• Lake Bonney (Taylor Valley)

• Lake Joyce (Pearse Valley)

• Lake Garwood (Garwood Valley)
• Lake Miers (Miers Valley)

Rivers

• Kite Stream (Victoria Valley)
• Onyx River (Wright Valley)
• Vincent Creek (Taylor Valley)
• Crescent Stream (Taylor Valley)
• Harnish Creek (Taylor Valley)
• Huey Creek (Taylor Valley)

See also

• John Charles Priscu

References

1. ^ Rejcek, Peter (November 29, 2007). "In the cold of the night" (web). Science team to extend seasonal work until April to study lake ecosystem in the McMurdo Dry Valleys. The Antarctic Sun. http://antarcticsun.usap.gov/science/contenthandler.cfm?id=1283. Retrieved 2008-01-13. 
2. ^ Bockheim, J. G. (2002). "Landform and Soil Development in the McMurdo Dry Valleys, Antarctica: A Regional Synthesis" (web). Arctic, Antarctic, and Alpine Research (Arctic, Antarctic, and Alpine Research, Vol. 34, No. 3) 34 (3): 308–17. doi:10.2307/1552489. JSTOR 1552489. http://instaar.colorado.edu/AAAR/browse_abstracts/abstract.php?id=2113. Retrieved 2008-09-26. 
3. ^ Lloyd, J & Mitchinson, J: "The Book of General Ignorance". Faber & Faber, 2006.
4. ^ John Timmer. Ancient, frozen ecosystem produces blood-red ice flows, Ars Technica, 16 April 2009. Accessed 17 April 2009.
5. ^ Mikucki, Jill A.; Ann Pearson, David T. Johnston, Alexandra V. Turchyn, James Farquhar, Daniel P. Schrag, Ariel D. Anbar, John C. Priscu, and Peter A. Lee (17 April 2009). "A Contemporary Microbially Maintained Subglacial Ferrous "Ocean"". Science 324 (5925): 397–400. doi:10.1126/science.1167350. PMID 19372431. http://www.sciencemag.org/cgi/content/abstract/324/5925/397. Retrieved 2009-04-21. 
6. ^ http://www.antarcticanz.govt.nz/downloads/environment/Map%20A%20McMurdo%20Dry%20Valleys%20Area.pdf

External links

Media related to McMurdo Dry Valleys at Wikimedia Commons

• Map of the McMurdo Dry Valleys area (pdf)
• Another map (USGS)
• Antarctic Connection
• Study: Life in Antarctic ice may compare to Mars
• Special Report: The McMurdo Dry Valleys, Antarctic Sun, January 26, 2003, 7–21.
• Virtual Tour of the Dry Valleys
• In Antarctica's Dry Valleys, worms offer clues to alarming changes in ecosystem - The New York Times/International Herald Tribune, November 2006
• A long-term ecological research group is working in the area.
• Pictures from the Dry Valleys
• Satellite images