Report on East Gakkel Ridge at 85°E (Undersea Features) — March 2001
Bulletin of the Global Volcanism Network, vol. 26, no. 3 (March 2001)
Managing Editor: Richard Wunderman.
East Gakkel Ridge at 85°E (Undersea Features) Two recently active volcanoes discovered beneath Arctic Ocean pack ice
Please cite this report as:
Global Volcanism Program, 2001. Report on East Gakkel Ridge at 85°E (Undersea Features). In: Wunderman, R. (ed.), Bulletin of the Global Volcanism Network, 26:3. Smithsonian Institution. https://doi.org/10.5479/si.GVP.BGVN200103-377020.
East Gakkel Ridge at 85°E
85.608°N, 85.25°E; summit elev. -3800 m
All times are local (unless otherwise noted)
A sonar survey along the ultraslow-spreading Gakkel Ridge by the USS Hawkbill submarine revealed two previously undiscovered volcanoes beneath the pack ice of the Arctic Ocean. Lineated magnetic anomalies over the entire ridge suggested that seafloor volcanism occurred there, but theoretical modeling predicted that melt production should be extremely low given the ~1.0-1.3 cm/year rate at which the ridge spreads. Sidescan and bathymetric data from the East Gakkel Ridge survey showed two amorphously shaped topographic highs with 1,000 m (eastern volcano) and 500 m (western volcano) of relative relief, with a highly reflective acoustic character. The high reflectivity was interpreted to indicate a lack of significant sedimentary cover on young basaltic flows.
Edwards and others (2001) reported that "portions of the strongly reflective regions . . . abut lineaments, consistent with the ponding of lava against fault scarps. Terminations of acoustically reflective terrain in regions devoid of lineaments have shapes characteristic of lava flow fronts . . .. These flow toes are radially distributed about the two topographic highs. The morphology of the strongly reflective regions is consistent with submarine volcanic flow systems mapped at other mid-ocean ridges by acoustic and optical [methods] . . . . The two acoustically reflective regions are thus probably volcanoes that are largely devoid of sediment cover, and therefore erupted recently. The presence of these two young volcanoes covering approximately 20% of the 3,750 km2 surveyed along . . . the eastern Gakkel Ridge, proves that significant volcanism occurs at ultraslow spreading rates."
During January-September 1999 global seismic networks detected an earthquake swarm corresponding to the approximate location of the W volcano discovered along the East Gakkel Ridge (86°N, 85°E). About 75% of the swarm occurred before the end of May. Edwards and others (2001) noted that "The correlation between the locations of the earthquake epicenters and the location of the strongly reflective, untectonized W volcano together with the volcanic character of the seismic record provide evidence that lava erupted on the E Gakkel Ridge . . . . Because 12-kHz sonars can penetrate through thin sediments covering acoustically reflective lavas, it is possible that no eruption occurred on Gakkel Ridge in 1999; however, historical global seismic records indicate that this is the only earthquake swarm detected on Gakkel Ridge in about 100 years."
Reference. Edwards, M.H., Kurras, G.J., Tolstoy, M., Bohnenstiehl, D.R., Coakley, B.J., and Cochran, J.R., 2001, Evidence of recent volcanic activity on the ultraslow-spreading Gakkel Ridge: Nature, v. 409, no. 6822, p. 808-812.
Geologic Background. During January-September 1999 global seismic networks detected an earthquake swarm along the East Gakkel Ridge (near 86°N, 85°E). Sonar mapping in May 1999 identified a cone at the western end of a line of volcanoes that corresponded to the average location of the epicenters (Edwards et al., 2001). A survey in July 2007 (Sohn et al., 2008) provided detailed bathymetry and named selected features, including the Oden (location of the 1999 seismicity), Thor, and Loke cones. Both Oden and Loke were covered with a light dusting of pyroclastic material, which was also found throughout the survey area, thought to be products of an eruption during the 1999 swarm.
Information Contacts: M.H. Edwards, Hawaii Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawaii at Manoa, POST 815, 1680 East-West Road, Honolulu, Hawaii 96822 USA (URL: http://www.soest.hawaii.edu/HMRG/cms/).