The world's largest iceberg appears to have run aground off the coast of a remote British island home to millions of penguins and seals — potentially threatening local wildlife, but also providing an opportunity for research into such rare "megabergs.

The A23a iceberg is twice the size of Greater London, and slightly smaller than the State of Rhode Island The world’s largest iceberg has run aground off the coast of a remote island in the Atlantic Ocean,

A23a weighs nearly a trillion metric tons, making it the world’s largest active iceberg. It calved from Antarctica in 1986, making it the world’s oldest berg. And now, after drifting for half a decade, A23a has grounded itself about 56 miles (90 kilometers) south of South Georgia.