Seismoacoustic evidence for volcanic activity on the ultraslow-spreading Gakkel Ridge, Arctic Ocean

[1] In 1999, a swarm of earthquakes and a lava flow signaled a volcanic eruption at the eastern end of Gakkel Ridge, the slowest spreading ridge worldwide. In summer 2001, the multidisciplinary Arctic Mid-Ocean Ridge Expedition studied these ridge processes which are unusual at ultraslow spreading rates. As part of these studies, we examined the microearthquake activity of the ridge with seismological arrays on ice-floes. Near the volcanic center (85°40′N 85°E) active in 1999, we recorded a remarkable swarm of 200 acoustic events. The signals consist of two to four explosive phases, representing the direct water wave and multiple reflections. We localized the acoustic source at the northern rim of the lava flow of 1999. By comparison with similar signals produced at the ocean entry of the Kilauea lava, we postulate that we made an exceptional observation of the sounds of active submarine volcanism.