Iceland

Image of free air gravity.

Click on the above free air gravity image to see a full-size version.

Vestmannaeyjar bathymetry.

Click on the above Vestmannaeyjar bathymetry image to see a full-size version.

Reykjanes Ridge EM300 backscatter data.

Click on the above Reykjanes Ridge EM300 backscatter data to see a full-size version.

The position of Iceland over the Mid-Atlantic Ridge is an ideal setting in which to investigate mid-ocean ridge processes and the effects of hotspots on these processes. Iceland is one of only two places on Earth where a seafloor spreading center rises above sea level, which allows work on the ridges to be placed in the extensive geological and geophysical context established for subaerial Iceland. The reorganizing plate boundaries in Iceland show some characteristics of propagating rifts and microplate tectonics

In July–August 2003 we conducted brief marine geophysical investigations of both Vestmannaeyjar and the Reykjanes Ridge. This was a collaborative effort with Ármann Höskuldsson of the University of Iceland, Neal Driscoll of the Scripps Inst. of Oceanography, and Bob Detrick of the Woods Hole Oceanographic Inst. We used the SIO SUBSCAN chirp seismic system to collect seismic profiles and sidescan sonar swaths, and the Iceland EM300 system to acquire swath bathymetry and backscatter data. Vestmannaeyjar, including the recently active eruptive centers of Surtsey and Heimaey, may be forming at the tip of the reorganizing North America-Eurasia plate boundary system, where the seafloor spreading on Iceland appears to be shifting from the Western Volcanic Zone to the Eastern Volcanic Zone (EVZ). A linear chain of small islands and seafloor eruptions is consistent with Vestmannaeyjar being the southern extension of the EVZ. The seafloor volcanic pattern shows large spatial variability, with only a few indications of tectonic rift structures seen in either the seafloor or subsurface data. If this is the tip of a propagating rift, the rifting has not yet focussed the volcanic eruptions into a single coherent eruptive segment. In contrast to Vestmannaeyjar, a brief EM300 survey of the first Reykjanes Ridge segment offshore of the Reykjanes Peninsula shows that seafloor spreading here has been active long enough that the volcanism has coalesced into a focussed volcanic system. Few rift structures are visible here either, perhaps because shallow explosive eruptions tend to bury them. The approximately 20 degree change in azimuth between the en echelon volcanic system trends on the Reykjanes Peninsula and those observed on the Reykjanes Ridge occurs within this first offshore segment.

Our future research will include a large-scale survey of the Reykjanes Ridge system, presently scheduled for summer 2007, to determine how this system has evolved and responded to the known plate boundary reorganizations on land. Our goal is a seamless history of the plate boundary geometry both at sea and on land, an essential step toward the full understanding of Iceland and the geodynamic influence of the hotspot or mantle plume on the mid-ocean ridge system.

Publications

  • Höskuldsson, A., R. Hey, E. Kjartansson, G.B. Gudmundsson, The Reykjanes Ridge between 63°10'N and Iceland, J. Geodynamics, 43, 73-86, 2007.

Oceanographic Expeditions

  • **2003 July: High-resolution chirp SUBSCAN seismic reflection survey of Vestmannaeyjar, Iceland, Reykjavik-Heimaey, University of Hawaii/WHOI/SIO/University of Iceland, chief scientist R.N. Hey, R/S BJARNI SAEMUNDSSON.
  • *2003 July–August: EM300 survey of Vestmannaeyjar and the Reykjanes Ridge, Iceland, Heimaey-Reykjavik, University of Iceland/ University of Hawaii/WHOI/SIO, chief scientist A. Höskuldsson, R/S ARNI FRIDRIKSSON.

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