An Advanced Submarine Cabled Observatory on Axial Seamount: Real-time Interaction with an Active Underwater Volcano Through the Internet

Abstract:

In 2014, the US first plate-scale submarine cabled observatory became operational as part of the US National Science Foundations' Ocean Observatories Initiative. Known as the Cabled Array, this facility includes 900 km of high-power (8 kW) and high-bandwidth (10 Gbs) fiber optic cables that span the Juan de Fuca tectonic plate. One branch of the system extends ~480 km west of Pacific City, Oregon to Axial Seamount, the largest and most active volcano on the intermediate-spreading Juan de Fuca Ridge. Here, two seafloor substations, eight junction boxes, >2300 m of extension cables, >54 instruments, and two state-of-the-art full water column moorings hosting instrumented wire crawlers, winched science pods, and platforms provide unprecedented real-time investigation of process linkages at the summit of the volcano and in the overlying water column on the volcanoe's flank. Two-way 24/7/365 communication through the Internet, allows rapid, highly interactive adaptive monitoring of volcanic eruptions and diking events. In concert, this array makes Axial Seamount the most advanced underwater volcanic observatory in the oceans.

Within the caldera, specialized seafloor sensors include high definition video and digital still cameras that provide stunning imagery of hydrothermal vents and associated biological communities, temperature-resistivity-pH-H₂S probes to examine boiling and subseafloor chemical reactions, a mass spectrometer, 3D thermistor arrays, and fluid and microbial DNA samplers. In concert, these sensors provide information on the impact of flow perturbations and chemistry associated with eruptive and seismic events on the biological communities. Broadband and short-period seismometers and low frequency hydrophones monitor seismic events associated with magma migration and eruptions and pressure-tilt meters measure inflation and deflation. The power of the Cabled Array was highlighted April 24, 2015 when data streaming live from the array detected a 10 hr seismic crisis involving >8,000 earthquakes coincident with an ~ 2.4 m collapse of the caldera floor. On April 26, thousands of impulsive events along the northern rift system marked the eruption of a 127 m thick, >7 km long lava flow. The flow summit was covered by acres of microbial mats bathed in warm fluids exiting the cooling flow.