Mid-ocean ridge volcanism generates two-thirds of the surface of our planet and plays an important role in chemical exchange with the overlying ocean, yet little is known about the dynamic processes involved in mid-ocean ridge eruptions. This is largely due to the costs and challenges of deploying long-term instrumentation on the seafloor, particularly those that transmit data to shore in real time and would allow the scientific community to respond to and coalesce around a particular event. The 2015 eruption at Axial Seamount, which lies along the Juan de Fuca Ridge in the Northeast Pacific Ocean, resulted in the first in situ, real-time geophysical data collected during a mid-ocean ridge eruption. The results provided insights into the caldera fault structure and response to a seafloor-spreading episode, and also confirmed the origin of seismically recorded impulsive signals that are associated with fresh lava erupting onto the seafloor. This confirmation of a seismic signal associated with erupting lava led to revisiting data from an eruption almost a decade earlier and a fundamental new view of seafloor spreading at fast-spreading ridges thousands of kilometers from Axial Seamount. This example illustrates the point that even though cabled observatories are necessarily bound to a specific location, their results can have significant implications for understanding systems that are quite different, in far reaches of the globe.

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