The McMurdo Dry Valleys are a row of valleys in Antarctica located within Victoria Land west of McMurdo Sound. In Geology, a valley (also called a vale, dale, glen or strath and near or in Appalachia, a draw) is Victoria Land is a region of Antarctica bounded on the east by the Ross Sea and on the west by Wilkes Land. The ice-clogged waters of Antarctica's McMurdo Sound extend about 55 km (35 mi long and wide  The region includes many interesting geological features including Lake Vida and the Onyx River, Antarctica's longest river. Lake Vida lies in Victoria Valley, one of the McMurdo Dry Valleys, on the continent of Antarctica. The Onyx River is a meltwater stream which flows westward through the Wright Valley from Wright Lower Glacier to Lake Vanda, during a few months of the Antarctic It is also one of the world's most extreme deserts. A desert is a Landscape or region that receives very little precipitation. From north to south, the three main valleys are Victoria Valley, Wright Valley and Taylor Valley. The Wright Valley is one of several Dry Valleys in the Transantarctic Mountains, located west of McMurdo Sound at approximately. The valleys cut through the Beacon sandstone. The Beacon sandstone is a geological formation exposed in Antarctica and deposited from the Devonian to the Triassic (~)
The Dry Valleys are so named because of their extremely low humidity and their lack of snow or ice cover. Humidity is the amount of water vapor in the air In daily language the term "humidity" is normally taken to mean Relative humidity. Together, at 4800 square kilometers, they constitute around 2% of the continent, and form the largest relatively ice-free region in Antarctica. The valley floors are covered with a loose gravelly material, in which sand-wedge polygons may be observed. Gravel is rock that is of a specific Particle size range In Geology, gravel is any loose rock that is larger than two millimeters (2mm
The unique conditions in the Dry Valleys are caused by katabatic winds (from the Greek word for 'going down'). A katabatic wind, from the Greek word katabatikos meaning "going downhill" is the technical name for a drainage Wind, a wind These occur when cold, dense air is pulled downhill simply by the force of gravity. The winds can reach speeds of 320 km/h (200 mph) evaporating all moisture - water,ice and snow - in the process. 
The gravel appears to be derived from two sources. The first is terminal moraines which have formed at the end of glaciers which descend into the Dry Valleys. A terminal moraine, also called end moraine, is a Moraine that forms at the end of the Glacier called the snout These glaciers sublime directly to air, for the most part, adding very little liquid water to the valleys. The second potential source of gravel is a rather unusual source. It is believed that during some glacial periods, the quantity of ice in the nearby Ross Sea was so great that it forced its way inland into some of the Dry Valleys, in a kind of reverse glacier and deposited its own terminal moraine. NOAA Ross seajpg|thumb|200px|thumb|Ice in the Ross Sea Antarctica]] The Ross Sea is a deep bay of the Southern Ocean in Antarctica between Victoria
Endolithic plants have been found living in the Dry Valleys, sheltered from the dry air in the (relatively) moist interior of rocks. An endolith or cryptoendolith is an Organism ( Archaeum, Bacterium, Fungus, Lichen, Alga or Amoeba Summer meltwater from the Valleys' overhanging glaciers provides the primary source of soil nutrients. "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. Scientists consider the Dry Valleys perhaps the closest of any terrestrial environment to Mars, and thus an important source of insights into possible extraterrestrial life. Extraterrestrial life is Life originating outside of the Earth.
Part of the Valleys was designated an environmentally protected area in 2004.