Axial Science Background
Axial Seamount is, scientifically, one of the most exciting parts of the OOI cabled system. Located on the western edge of the Juan de Fuca Plate and located at the summit of a shallow portion of the Juan de Fuca spreading center, Axial is the locus of a highly active volcano-hydrothermal system.
For several years researchers (Chadwick and Nooner) have been monitoring the inflation and deflation of Axial Seamount using uncabled seafloor pressure sensors. Data were analyzed following recovery of the instruments. Following eruptions in 1998 and 2011, they documented inflation of the summmit of Axial due to increasing pressure within the underlying magma chamber about 2 km below the seafloor. An especially exciting observation since 2012, by the same authors, was that the rate of rise of the caldera floor suddenly increased by a factor of 4, from an average of 15 cm/year to nearly 60 cm/year at the center of the caldera.
In 2014, with installation of the Cabled Array, a revolution occurred that now allows a global community to monitor the volcano in real-time. There are 21 geophysical, geochemical, and biological sensors now installed at the summit of Axial Seamount providing co-registered, live streaming data at unprecedented bandwidth. This includes 3 cabled bottom pressure-tilt instruments built by Chadwick's group. Real-time data flow in 2014 to early 2015 showed unprecedented increases in inflation indivative of melt and volatile injection beneath the caldera.
On Axial 24, 2015, William Wilcock, through hourly monitoring of seismic data from cabled seismometers on the volcano indicated "Quite a few earthquakes are now visible at the base of Axial, so I think this swarm si also more significant in terms of moment release". Indeed, over 8000 earthquakes were detected over a 24 hr period, and over this same interval the bottom pressure-tilt instruments showed that the seafloor dropped >7 ft - the volcano was erupting! For the first time, scientists from across the country were able to "watch and hear" an underwater volcano erupt live from >300 miles offshore and 5000 ft beneath the oceans' surface. Hydrophones detected implosive events that are interpreted to result from the explosions of pillow basalts as they are extruded onto the seafloor (Wilcock and Garcia).
During the Cabled Array VISIONS'15 Operations and Maintenance cruise, the area where hundreds of impulsive events was mapped on the northern rift system of the voclano. A bathymetric difference map showed documented a >400 ft change in elevation of the seafloor - equivalent to 2/3 the height of the Seattle Space Needle. A follow-on dive, with the robotic vehicle ROPOS, the science party layed the first eyes on the 3-month old eruption. Acres of microbial mats covered the summit of the new lava flow, fed by warm, volatile-rich fluids circulating through the thick lava flow.
For the first time, members of the science community interested in submarine volcanism and hydrothermal activity are remotely witnessing the complex processes leading up to an eruption, the actual eruption, and the transition from eruption to post-eruption. Scientists on land and instruments on site are capable of two-way communication at the speed of light (lasers on optical fiber) through connection to the Internet. This is an entirely novel opportunity for scientists and the public alike to observe the prelude, event, and denouement of an Axial Seamount eruption.