Evidence of recent volcanic activity on the ultraslow-spreading Gakkel ridge

Seafloor spreading is accommodated by volcanic and tectonic processes along the global mid-ocean ridge system. As spreading rate decreases the influence of volcanism also decreases, and it is unknown whether significant volcanism occurs at all at ultraslow spreading rates (<1.5 cm yr-1). Here we present three-dimensional sonar maps of the Gakkel ridge, Earth's slowest-spreading mid-ocean ridge, located in the Arctic basin under the Arctic Ocean ice canopy. We acquired this data using hull-mounted sonars attached to a nuclear-powered submarine, the USS Hawkbill. Sidescan data for the ultraslow-spreading (∼1.0 cm yr-1) eastern Gakkel ridge depict two young volcanoes covering approximately 720 km2 of an otherwise heavily sedimented axial valley. The western volcano coincides with the average location of epicentres for more than 250 teleseismic events detected in 1999, suggesting that an axial eruption was imaged shortly after its occurrence. These findings demonstrate that eruptions along the ultraslow-spreading Gakkel ridge are focused at discrete locations and appear to be more voluminous and occur more frequently than was previously thought.

[1]  T. Simkin,et al.  Caldera Collapse in the Galapagos Islands, 1968: The largest known collapse since 1912 followed a flank eruption and explosive volcanism within the caldera. , 1970, Science.

[2]  H. Paul Johnson,et al.  The geological interpretation of side‐scan sonar , 1990 .

[3]  F. Gasse,et al.  Contemporary, Holocene, and Quaternary deformation of the Asal Rift, Djibouti: Implications for the mechanics of slow spreading ridges , 1991 .

[4]  Y. Kristoffersen.  The Nansen ridge, Arctic Ocean; some geophysical observations of the rift valley at slow spreading rate , 1982 .

[5]  Yongshun John Chen.  Oceanic crustal thickness versus spreading rate , 1992 .

[6]  J. Sinton,et al.  Geochemical diversity of the large lava field on the flank of the East Pacific Rise at 8°17′S , 1996 .

[7]  W. Chadwick,et al.  Evidence for volcanic eruption on the southern Juan de Fuca ridge between 1981 and 1987 , 1991, Nature.

[8]  Deborah K. Smith,et al.  Constructing the upper crust of the Mid-Atlantic Ridge : A reinterpretation based on the Puna Ridge, Kilauea Volcano , 1999 .

[9]  H. Jackson,et al.  Oceanic spreading rate and crustal thickness , 1981, Marine Geophysical Researches.

[10]  Robert J. Urick,et al.  Principles of underwater sound , 1975 .

[11]  J. R. Cochran,et al.  Gravity evidence of very thin crust at the Gakkel Ridge (Arctic Ocean) , 1998 .

[12]  R. White,et al.  Variation with spreading rate of oceanic crustal thickness and geochemistry , 1994 .

[13]  S. Laxon,et al.  Arctic Ocean Gravity Field Derived From ERS-1 Satellite Altimetry , 1994, Science.

[14]  G. Johnson,et al.  Detailed aeromagnetic investigation of the Arctic Basin , 1979 .

[15]  Walter H. F. Smith,et al.  Global Sea Floor Topography from Satellite Altimetry and Ship Depth Soundings , 1997 .

[16]  Robert D. Ballard,et al.  Morphology and tectonics of the inner rift valley at lat 36°50′N on the Mid-Atlantic Ridge , 1977 .

[17]  P. Vogt,et al.  Volcanic and Seismic Swarm Events on the Reykjanes Ridge and Their Similarities to Events on Iceland: Results of a Rapid Response Mission , 1997 .

[18]  K. Macdonald,et al.  A 220 km2 recently erupted lava field on the East Pacific Rise near lat 8°S , 1989 .

[19]  Richard G. Gordon,et al.  Current plate motions , 1990 .

[20]  C. Müller,et al.  Seismic evidence for volcanic activity discovered in central Arctic , 2000 .

[21]  E. Parmentier,et al.  Three‐dimensional mantle convection beneath a segmented spreading center: Implications for along‐axis variations in crustal thickness and gravity , 1993 .