An iceberg containing enough water for everyone on the planet for a year has broken away from Antarctica.

The 78 kilometre long iceberg has a surface area of roughly 2,500 square kilometres, which is about five times the size of the Nelson District.

It is 400 metres thick, and weighs one billion tonnes.

Glaceologist Neal Young says scientists have put GPS devices on it, to track what happens next. Scientists say the big berg is not a product of climate change, although it is a once in a 50-year event.

It broke away after a collision with another large iceberg on the Mertz glacier.