# What is the mechanism for deep-sea volcanism of the Gakkel Ridge in the Arctic?

Related to an earlier question, What is the geochemical source for the helium detected in deep Arctic explosive eruptions?, where it is stated in the linked article that there is evidence of explosive volcanism deeper than 3km depth - the evidence coming from both seismic and petrological observations. The article Hotbed of Volcanic Activity Found Beneath Arctic Ocean suggests that, as the article title alludes to, that the region has many hydrothermal vents and explosive centres.

These types of eruptions are not thought to be able to occur at depths greater than 3km, according to the article Arctic Volcanoes Found Active at Unprecedented Depths.

What is the mechanism for deep-sea explosive volcanism of the Gakkel Ridge in the Arctic?

According to the article Explosive volcanism on the ultraslow-spreading Gakkel ridge, Arctic Ocean (Sohn et al. 2008), to overcome the pressure of the seawater, it becomes a question of the amount of volatiles (particularly $\ce{CO2}$ available in the magma chamber to cause fragmentation resulting in the glassy pyroclastic deposits observed around the volcanic centres on the Gakkel Ridge.
The long interval times allow for the accumulation of large volumes of volatiles in the upper part of the magma chambers. These would erupt periodically when the pressure in the magma chamber exceeds the deep sea-water pressure. Models from Sohn et al. suggest that a weight fraction of 14% $\ce{CO2}$ (~75% volume fraction) would be required - a value considerably higher than those measured at most mid ocean ridges. Pontbriand et al. estimate that $\ce{CO2}$ supersaturation in the magma chambers of the Gakkel Ridge to occur around 1500-2000 year timeframes (i.e. well within the estimated volcanism interval).