The world’s largest iceberg, which broke off a West Antarctica ice shelf in 1986 and has been has been stuck in place for decades, is drifting. The 1,500-square-mile, trillion-ton mass has been immobile in the Weddel Sea until now. “Over time it’s probably just thinned slightly and got that little bit of extra buoyancy that’s allowed it to lift off the ocean floor and get pushed by ocean currents,” British Antarctic Survey glaciologist Oliver Marsh told Reuters. Experts said the berg, called A23a, could end up taking “iceberg alley” to the Southern Ocean or get stranded at South Georgia island, where it would be a hazard to wildlife.