A massive crack in one of Antarctica's largest ice shelves has created an iceberg bigger than Kangaroo Island.

The Larsen C ice shelf is located on the Antarctic Peninsula, which juts out towards South America.

The large fracture, which has been growing across the ice sheet for decades, recently started to accelerate, said Sue Cook, a glaciologist from the Antarctic Climate and Ecosystems Cooperative Research Centre.

According to the latest data by a team of UK scientists, the fracture ripped open by 17 kilometres in the last week of May and turned towards the ocean.

It has created an iceberg of 5,800 square kilometres.

Sorry, this video has expired Aerial footage shows a massive iceberg has broken away from a key floating ice shelf in Antarctica

What is an ice shelf?

An ice shelf is a section of ice that juts out into the sea.

Snow from the interior builds up and flows out to the edge of the continent. At the edges it thins, and because ice is less dense than water, it sits on top of the ocean instead of on the sea bed.

"So you have this transition from where the ice is on ground moving to a point where it is moving out into the ocean."

The anatomy of an ice shelf. ( Supplied: Dr Sue Cook )

What happens when an iceberg breaks off?

The iceberg is massive, so it's been a slow process.

"You might have seen videos of icebergs up in Greenland and they crash and roll and turn in [a] very violent process," Dr Cook told the World Today.

"In Antarctica, it doesn't tend to be quite as sudden or as dramatic. They move away much more slowly from the ice shelf."

What impact will it have on the ice shelf?

The Larsen C ice shelf, which is Antarctica's fourth largest ice shelf, covers an area of 46,500 square kilometres.

"The iceberg that's about to come off will be about 10 per cent of the ice shelf area," Dr Cook said, speaking ahead of the ice shelf fracture.

It's normal for icebergs to break off ice shelves.

"Ice shelves are constantly flowing into the ocean, losing a bit off the end," she said.

"It might not really have a big impact on the [stability of the] ice shelf."

But, she said, it could also destabilise the ice shelf causing it to quickly disintegrate.

The rift in Antarctica's Larsen C ice shelf up close. ( Supplied: NASA )

That's exactly what happened in 2002 to the neighbouring ice shelf Larsen B.

"One large iceberg came off the front of it — then during the next summer the whole thing splintered and the whole thing washed out to sea within the space of two or three months," Dr Cook said.

Could this affect sea levels?

This iceberg itself won't increase sea levels because it is breaking off from floating ice.

But there will be increases in sea levels if the entire ice shelf breaks up.

"If you remove an ice shelf, all of the glaciers that used to feed into it start putting more ice out into the ocean and that's where you get your potential contributions to sea level rise," Dr Cook said.

Two large sections of the ice shelf (Larsen A and B) have collapsed within the past three decades. ( Supplied: NASA )

She said when the Larsen B ice shelf disintegrated in 2002, the glaciers that flowed into it more than doubled in speed.

"If the Larsen C were to collapse, then we'd expect to see a similar acceleration of its tributary glaciers," Dr Cook said.

She said the glaciers feeding into the Larsen C ice shelf contained about 10 centimetres of global sea level equivalent, but it's very unlikely that all of that would go.

What's causing it to happen?

Dr Cook said it was really hard to pin down exactly why this is happening.

The Antarctic Peninsula is rapidly warming, but there is no evidence to link the cracking of the ice shelf to climate change.

"In this case it is really hard to say whether it has something to do with global warming or not," Dr Cook told the World Today.

"Icebergs are constantly being released, and with the short record sometimes it's hard to tell what is a normal rate and what isn't. But this one's particularly large."

Dr Cook said now this iceberg calved, the front of the shelf has moved back to the furthest point that's ever been recorded.

"So that implies that there is a process that is causing it to move more ice than it has in the past," she said.

How are we monitoring the ice shelf?

Scientists are monitoring the ice shelf using radar data from satellites.

But Dr Cook said there was no way to reliably predict when an ice shelf would break up.

"It's one of the things we'd like to be able to do better, because all of our sea level rise predictions could be affected quite a lot by this."