McMurdo Dry Valleys

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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[edit]

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[edit]

ASTER image of the Dry Valleys.

The valleys cut through the Beacon Supergroup, as well as older granites and gneisses of the Ross Orogeny. Deposited directly from ice, tills dot this bedrock landscape. These 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.

Life[edit]

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. It was previously thought that the algae was staining red the ice emerging at Blood Falls but it is now known that the staining is caused by high levels of iron oxide.[4][5]

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

Major geographic features[edit]

Valleys[edit]

From north to south, the three main valleys are

West of Victoria Valley are, from north to south,

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

West of Taylor Valley is

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:

Lakes[edit]

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.

Rivers[edit]

See also[edit]

References[edit]

  1. ^ Rejcek, Peter (29 November 2007). "In the cold of the night". The Antarctic Sun. Retrieved 2008-01-13. 
  2. ^ Bockheim, J. G. (2002). "Landform and Soil Development in the McMurdo Dry Valleys, Antarctica: A Regional Synthesis". Arctic, Antarctic, and Alpine Research 34 (3): 308–317. doi:10.2307/1552489. JSTOR 1552489. (subscription required (help)). 
  3. ^ Lloyd, John; Mitchinson, John (2006). The Book of General Ignorance. Faber & Faber. 
  4. ^ Timmer, John (16 April 2009). "Ancient, frozen ecosystem produces blood-red ice flows". Ars Technica. Retrieved 17 April 2009. 
  5. ^ Mikucki, Jill A.; Pearson, Ann; Johnston, David T.; Turchyn, Alexandra V.; Farquhar, James; Schrag, Daniel P.; Anbar, Ariel D.; Priscu, John C.; Lee, Peter A. (17 April 2009). "A Contemporary Microbially Maintained Subglacial Ferrous "Ocean"". Science 324 (5925): 397–400. doi:10.1126/science.1167350. PMID 19372431. Retrieved 2009-04-21. (subscription required (help)). 
  6. ^ "Map of the McMurdo Dry Valleys Area" (pdf). Antarctica New Zealand. Archived from the original on 2009-03-27. 

External links[edit]