A huge iceberg that will grow to 880 square kilometres - an area the size of Berlin - is forming in a shelf of floating ice in West Antarctica.
The iceberg started out as a surface crack in the sheet of ice, which is located in front of the Pine Island Glacier (PIG) in the Antarctic region.
The rift, which was first noticed in October, runs for almost 20 miles from end to end and is thought to be 200ft deep.
With the crack widening every day, the iceberg will be formed - or 'calved' as it is scientifically known - when it breaks away from the floating ice mass.
This is expected to take place at the end of the year or in early 2012.
Scientists from the US space agency (Nasa) say the fully-formed iceberg will cover an area of around 880 square kilometres, the same size as the German capital city.
PIG is one of the largest and fastest-moving masses of ice in the Antarctic, and is responsible for around a tenth of all the ice flowing into the world's oceans.
In recent years, satellites have recorded a noticeable thinning of the glacier, which many have linked to climate change and global warming.
But scientists monitoring the calving of the giant iceberg say the new formation is part of a 10-year cycle that occurs naturally.
"The last big calving event occurred in 2001 so in general people have been expecting something like this to happen fairly soon, and for us it is very exciting to see this while it is happening," Dr Michael Studinger, a scientist from Nasa's IceBridge project, told BBC News.
"Eventually, the iceberg will move further north; it will be picked up by wind and ocean currents - and the primary ocean current there is the Antarctic Circumpolar Current. We will certainly be following it."
Calving is a form of ice disruption, caused by the sudden release and breaking away of a mass of ice from a glacier or larger iceberg.
The phenomenon is usually preceded by a rift in a larger mass of ice, and is preceded by a large cracking sound before the new mass breaks loose.
Calving produces up to 15,000 new icebergs each year in Greenland alone, and has become a popular tourist attraction in Alaska.