This book presents an in-depth review of El Hierro Island, the youngest and most southwesterly volcano of the Canary Islands. In October 2011, a submarine eruption started offshore El Hierro Island. The 2011�12 El Hierro eruption has probably been the best monitored and studied submarine eruption to date and has sparked interest in the study of this young ocean island volcano. During the last decade, multidisciplinary investigations, e.g., on the geological and volcanological character of its past and latest onshore and offshore eruptions, the geophysical and geochemical signatures of its magmatic plumbing system structure and dynamics, as well as the bio-geophysical interactions and consequences of submarine eruptions in the ocean, have been conducted. This book provides an authoritative review of many of these scientific advances as well as multiple remaining unknowns for the study of El Hierro Island and its 2011�12 submarine eruption. Such knowledge should be of great interest to specialists not only in the Canary Islands volcanism but also in similar ocean island intraplate volcanoes.