The Onyx River is a meltwater stream which flows westward through the Wright Valley

Wright Valley

The Wright Valley is the central one of the three large Dry Valleys in the Transantarctic Mountains, located west of McMurdo Sound at approximately . Wright Valley contains the Onyx River, the largest river in Antarctica, Lake Brownworth, the origin of Onyx River, and Lake Vanda, which is fed by...

 from Wright Lower Glacier

Wright Lower Glacier

Wright Lower Glacier is a stagnant glacier occupying the mouth of Wright Valley and coalescing at its east side with Wilson Piedmont Glacier, in Victoria Land. Formerly called Wright Glacier, but that name was amended by the Victoria University of Wellington Antarctic Expedition to distinguish...

 and Lake Brownworth

Lake Brownworth

Lake Brownworth is a meltwater lake immediately west of Wright Lower Glacier at the east end of Wright Valley, Victoria Land. The lake was mapped by the United States Geological Survey from surveys and air photos obtained in 1956–60. It was named by the Advisory Committee on Antarctic Names for...

 at the foot of the glacier to Lake Vanda

Lake Vanda

Lake Vanda is a lake in Wright Valley, Victoria Land, Ross Dependency, Antarctica. The lake is 5 km long and has a maximum depth of 69 m. On its shore, New Zealand maintained Vanda Station from 1968 to 1995...

, during a few months of the Antarctic summer.

The Onyx River is one of the many sites studied by the United States Antarctic Program

United States Antarctic Program

United States Antarctic Program is an organization of the United States government which has presence in the continent of Antarctica. It co-ordinates research and the operational support for research in the region...

 of the National Science Foundation

National Science Foundation

The National Science Foundation is a United States government agency that supports fundamental research and education in all the non-medical fields of science and engineering. Its medical counterpart is the National Institutes of Health...

. The river flow is away from the ocean as the Wright Glacier blocks the entrance to the valley. It is the largest river in Antarctica and, at 25 miles (40.2 km) in length, it is also the longest. It has several tributaries, and there are multiple meteorological stations along the length of the river. Flow levels are highly variable, both during the day and between summers, with the river failing to reach the lake some years. In contrast, it can cause significant erosion in flood years, and was rafted in 1984 by New Zealand researchers. While there are no fish in Onyx River, it does support microscopic life

Microorganism

A microorganism or microbe is a microscopic organism that comprises either a single cell , cell clusters, or no cell at all...

, and the algal bloom

Algal bloom

An algal bloom is a rapid increase or accumulation in the population of algae in an aquatic system. Algal blooms may occur in freshwater as well as marine environments. Typically, only one or a small number of phytoplankton species are involved, and some blooms may be recognized by discoloration...

s can be quite extensive. The Antarctica New Zealand

Antarctica New Zealand

Antarctica New Zealand is an Institute set up by the New Zealand Government in 1996 to manage its interests in Antarctica and the Ross Sea. As well as providing logistics support to a large scientific programme, it also runs bases such as Scott Base...

 program once maintained a semi-permanent camp at Lake Vanda which has since been removed. Currently there is a small research shelter at Lake Vanda at its eastern end. Nearby is the Comprehensive Test Ban Treaty

Comprehensive Test Ban Treaty

The Comprehensive Nuclear-Test-Ban Treaty bans all nuclear explosions in all environments, for military or civilian purposes. It was adopted by the United Nations General Assembly on 10 September 1996 but it has not entered into force.-Status:...

Seismic station at Bull Pass.