The world's largest underground lake that is a staggering 35 million years old

Lying an incredible 4,000 metres below the Antarctic is the world's largest underground lake. (Image: Getty)

Located approximately 2.5 miles beneath Russia’s Vostok Station on the East Antarctic Ice Sheet (EAIS), which sits at 3,488 metres above mean sea level, lies the largest of the continent’s 675 known subglacial lakes, which is also the largest in the world.

The surface of this freshwater lake is around 4,000 metres under the surface of the ice, which places it at approximately 500 metres below sea level.

Measuring 160 miles long by 30 miles wide at its widest point, it covers an area of 4,830 square miles, also making it the 16th largest lake in the world by surface area. With an average depth of 432 metres, it has an estimated volume of 1,300 cubic miles, making it the sixth largest lake by volume.

After decades of speculation and data gathering, the existence of the lake was confirmed in the mid-1990s by a combination of seismic and ice-penetrating radar surveys.

The age of the water in Lake Vostok is unknown, but some scientists believe it may be as old as 35 million years, created when the EAIS formed. Others think it may be as young as 400,000 years as the ice above the lake contains a paleoclimatic record (a natural archive of environmental change used to study past climates) of around this age.

Most scientists agree that Lake Vostok might harbour a unique freshwater ecosystem with independently evolved organisms. (Image: Nicolle Rager-Fuller / National Science Foundation)

The lake derives its name from Vostok Station, which in turn is named after the “Vostok”, a 18th- and 19th-century warship, which means “East” in Russian.

It is divided into two deep basins by a ridge, with a liquid water depth of roughly 400 metres in the northern basin and 800 metres in the southern.

While the lake’s age is up for debate, most scientists agree that Lake Vostok might harbour a unique freshwater ecosystem made up of organisms that evolved independently from other forms of life on earth.

The base of the lake’s food chain would need to derive its energy from chemical sources rather than from photosynthesis and each organism would need to ensure the pressure of 350 atmospheres, about 5,150 pounds per square inch, brought on by the weight of the ice sheet above.

Lake Vostok is also an oligotrophic extreme environment, one that is expected to be supersaturated with nitrogen and oxygen, 50 times higher than those typically found in ordinary freshwater lakes on Earth’s surface.

A picture c.1990s showing French, Soviet, and American scientists with unprocessed ice cores. (Image: Todd Sowers, LDEO, Columbia University, Palisades, New York)

Its conditions are thought to resemble those of ice-covered oceans hypothesised to exist on Jupiter’s moon Europa and Saturn’s moon Enceladus. Several scientists have remarked that the effort to reach Lake Vostok could be a valuable planning and implementation tool for future space missions designed to search for life on ice-covered worlds.

On February 5 2012, a team of Russian scientists completed the longest ever ice core of 3,768 m and pierced the ice shield to the surface of the lake.

The first core of freshly frozen lake ice was obtained on 10 January 2013 at a depth of 3,406 metres. However, as soon as the ice was pierced, water from the underlying lake gushed up the borehole, mixing it with the Freon and kerosene used to keep the borehole from freezing. A new borehole was drilled and an allegedly pristine water sample was obtained in January 2015.

The Russian team plans to eventually lower a probe into the lake to collect water samples and sediments from the bottom.

The coldest naturally occurring temperature ever observed on Earth, −89C, was recorded at Vostok Station on 21 July 1983. The average water temperature is calculated to be around −3C - it is understood to be able to remain in a liquid state below the normal freezing point because of high pressure from the weight of the ice above.

Geothermal heat from the Earth's interior may also warm the bottom of the lake, while the ice sheet itself insulates the lake from cold temperatures above.