Largest subglacial lake

The largest lake under a glacier is Subglacial Lake Vostok, which lies beneath almost 4 kilometres (2.5 miles) of ice under a region known as the "Pole of Cold", close to Russia’s Vostok research station, which also happens to hold the record for the world’s coldest naturally occurring temperature. Subglacial Lake Vostok is one of almost 400 lakes trapped beneath the Antarctic Ice Sheet and is 230 kilometres (143 miles) long and up to 50 kilometres (31 miles) wide. Its surface area of 14,000 square kilometres (5,405 square miles) makes it around 20 times larger than Lake Geneva. The water temperature is calculated to be a few degrees below zero, but remains in liquid form due to the high pressure of the overlying ice, which also insulates the lake from the freezing temperatures at the surface.

On 5 February 2012, after more than 20 years of drilling through the ice above Vostok Subglacial Lake, Russian scientists finally reached the surface of the lake at a depth of 3,768 metres (12,362 feet) beneath the ice. To avoid contaminating the lake water, the drill bit immediately withdrew and water from the lake rose 30–40 metres (98–131 feet) up the borehole before freezing. On 10 January 2013, the team successfully retrieved their first samples of this frozen lake water.