World's largest iceberg twice the size of London is heading straight for a British island

A trillion tonne iceberg which is twice the size of Greater London is headed on a collision course with a British island.

The world's largest iceberg has been dubbed a 'megaberg', though it also bears the more official name of A23a, and it first broke free of the Antarctic coastline all the way back in 1986.

Thankfully, it was so large that it spent the next three decades wedged in the Weddell Sea, but in 2020 it had become unanchored from the sea floor and went on the move again.

The iceberg is about twice the size of Greater London (UK MOD Crown Copyright via Getty Images)

It got stuck again in 2024 after becoming trapped in a vortex known as a 'Taylor Column', which is where rotating water traps an object in place to leave A23a stranded and in a spin for months.

Unfortunately, the world's largest iceberg started moving again and according to Sky News, is heading for a British island.

Fortunately, that island is South Georgia, which is situated in the South Atlantic Ocean and is home to only around 30 to 40 people.

But this gigantic megaberg still poses a significant danger to the many penguins and seals that call the island home with British Antarctic Survey physical oceanographer Andrew Meijer concerned that A23a could 'dramatically increase mortality rates' among penguins.

Meijer was able to closely study this giant iceberg in 2023 when he was on board the RRS Sir David Attenborough (the one that was originally going to be called Boaty McBoatface) and described it as 'a Game of Thrones-style wall of ice that towers above the ship'.

If the giant iceberg gets stuck in the shallow water around the island that could block paths penguins take to go and find food, meaning it's a more tiring thing for them and they bring back less food for their chicks.

Yesterday (23 January) the BBC reported that this gargantuan iceberg was 173 miles away from South Georgia and is under constant monitoring.

While the iceberg first broke off in 1986 the journey it is currently on is likely to spell doom for A23a.

Experts fear the iceberg could be devastating for the penguins that call South Georgia home, since it may mean they can't bring as much food to their chicks (Sascha Grabow/Getty Images)

That's because the further north it travels the warmer the water it will move through is and the process of it melting and breaking up will accelerate.

Satellite images indicate that the giant iceberg used to be about 1,500 square miles and has since shrunk to about 1,350 square miles, with experts predicting that it will eventually break up into smaller chunks which may cause problems of their own both for the local wildlife and the ships sailing through the area.