Axial Volcano, a large submarine volcano sitting on the Juan de Fuca spreading ridge, 250 miles off the Oregon coast, is one of the three sites of a major NSF investment in ocean observing. Due to its association with an important and unique hydrothermal vent system and its propensity for erupting on what appears to be a decadal time scale, Axial has also been the site of a 15 year NSF/NOAA time-series study of submarine volcanic activity. Axial is also the first and only site where active volcanic inflation has been documented on the seafloor and used to successfully forecast the timing of the next eruption. During a routine visit to the volcano in July of 2011, it was discovered that Axial had once again erupted and spewed lava flows more than 2 kilometers wide and many kilometers long across the seafloor, causing the floor of the caldera to subside by more than 2 meters. This research supports the collection of geophysical and geodetic measurements on the volcanic edifice to measure the rate at which magma refills the emptied magma chamber inside the volcano. Innovative undersea surveying methods, using a combination of newly established benchmarks and bottom pressure recorders will be used to monitor the long-term vertical deformation of the volcano. Results of this work extend the present time-series and allow us to refine and test models of both the eruption cycle behavior and of submarine volcano shallow magma dynamics and rheology. It will also help to allow us to assess how predictably the volcano behaves over several eruption cycles. Insights from the project will have applications for in both undersea technological advances as well as improving our understanding of the behavior of mid-ocean ridge magmatic systems and undersea volcanic hazards. Broader impacts of the work include the development of new techniques that build infrastructure for science and developing a better understanding of submarine volcanic hazards.
We conducted a research expedition with the Jason remotely operated vehicle in September 2013 to Axial Seamount, an active submarine volcano in the NE Pacific. The main goal of the project was to continue a time-series of innovative volcanic inflation/deflation measurements using precise pressure sensors to determine if and how much the seafloor in the summit caldera was bulging upward in response to magma accumulating at depth. These measurements have documented both gradual inflation (the seafloor moving upward) between eruption at rates of 15-60 cm/yr (6-23 inches/yr), and rapid deflations (the seafloor moving downward) during eruptions of 2-3 meters (6-10 feet). Axial Seamount is the only place in the world where these kinds of ground movements have been successfully documented at a submarine volcano and where that monitoring has been used to successfully forecast the timing of the next eruption. Our measurements in 2013 show that the inflation rate since the last eruption in 2011 was higher than expected. We measured 1.22 m of uplift at the caldera center since August 2011, totaling 1.57 m of reinflation since the April 2011 eruption. This was an average uplift rate of 61 cm/yr. For comparison, during most of the period between the 1998 and 2011 eruptions, we saw steady inflation at only 15 cm/yr. Overall, this means that Axial had already recovered 65% of the 2.4 m of deflation that we measured during the 2011 eruption. If this inflation rate continues, it will be back to its pre-2011 level of inflation within only another year and a half (by January 2015). An inescapable conclusion is that the inflation rate since 2011 has been higher than we’ve ever measured, and this implies that the next eruption will come considerably sooner than the previous recurrence interval of 13 years. These new results also indicate that Axial’s magma supply rate has significantly increased since 2011.
