During the summer of 2012, a raft of newly formed volcanic rock one and a half times the size of Boston appeared in the Pacific Ocean near New Zealand. It was scientists’ clue that a volcano was erupting deep below the sea surface. Five years later, scientists have released their first in-depth analysis of what appears to have been the largest eruption of its kind in the past century. Adam Soule is chief scientist for the National Deep Submergence Facility at Woods Hole Oceanographic Institution