Seafloor deformation and forecasts of the April 2011 eruption at Axial Seamount

Axial Seamount is an active submarine volcano located at the intersection between the Cobb hotspot and the Juan de Fuca spreading centre in the northeast Pacific Ocean1, 2. The volcano has been closely monitored since it erupted in 1998 (refs 3, 4). Since then, Axial Seamount seemed to exhibit a similar inflation–deflation cycle to basaltic volcanoes on land and, on that basis, was expected to erupt again sometime before 2014 or 2020 (refs 5, 6). In April 2011 Axial Seamount erupted. Here we report continuous measurements of ocean bottom pressure that document the deflation–inflation cycle of Axial Seamount between 1998 and 2011. We find that the volcano inflation rate, caused by the intrusion of magma, gradually increased in the months leading up to the 2011 eruption. Sudden uplift occurred 40–55 min before the eruption onset, which we interpret as a precursor event. Based on our measurements of ground deformation through the entire eruption cycle at Axial Seamount, we suggest that another eruption could occur as early as 2018. We propose that the long-term eruptive cycle of Axial Seamount could be more predictable compared with its subaerial counterparts because the volcano receives a relatively steady supply of magma through the Cobb hotspot and because it is located on thin oceanic crust at a spreading plate boundary.