After the North Magnetic Pole was located in 1831, explorers and scientists began looking for the South Magnetic Pole. James Clark Ross, a British naval officer, identified its approximate location, but was unable to reach it on his trip in 1841. Commanding the British ships Erebus and Terror, he braved the pack ice and approached what is now known as the Ross Ice Shelf, a massive floating ice shelf over high. His expedition sailed eastward along the southern Antarctic coast discovering mountains which were since named after his ships: Mount Erebus, the most active volcano on Antarctica, and Mount Terror.