The island appears to be primarily made out of mud from the seafloor, although photos show rocks as well, Barnhart told National Geographic. He has has been studying images and media accounts of the new island from his lab in Golden, Colorado.

“It brought up a dead octopus, and people have been picking up fish on [the island],” he said.

A similar mud island appeared off Pakistan after a 2011 earthquake there, Barnhart said: “It lasted a month or two and then washed away.”