HR: 1330h
AN: V22A-0564    [PDF]
TI: Submarine Tuff Cones at the Depth of 75 m South of Iceland: Evidence for Lower Sea Level During the Pleistocene
AU: * Hoskuldsson, A
EM: armh@hi.is
AF: University of Iceland, Geosciences, Sudurgata, Reykjavik, 101 Iceland
AU: Hey, R N
EM: hey@soest.hawaii.edu
AF: University of Hawaii, 2525 Correa Rd, Honolulu, HI 96822 United States
AU: Driscoll, N
EM: ndriscoll@ucsd.edu
AF: Scripps Inst. of Oceanography, GRD, La Jolla, CA 92093 United States
AU: Detrick, R
EM: rdetrick@whoi.edu
AF: Woods Hole Oceanographic Inst., 360 Woods Hole Rd, Woods Hole, MA 02543 United States
AB: Vestmannaeyjar archipelago, off the south coast of Iceland, marks the southernmost tip of the Eastern Volcanic Zone (EVZ) cutting Iceland in half from south to north. The EVZ marks the plate boundary between the American and Eurasian plates. It is believed that the plate boundary was relocated some 3 Ma ago and since has been propagating towards the south. Volcanism in the area of Vestmannaeyjar has been active during the Holocene with two major eruptive episodes, the former starting some 7-6 Ka ago and the second starting 1963 AD with the last eruption dating back some 30 years on the island of Heimaey, the largest island within the archipelago. In July-August 2003 we conducted brief surveys of the Vestmannaeyjar area to try to determine whether or not the recent volcanic eruptions here result from nascent plate boundary processes. We used the SIO SUBSCAN chirp seismic system to collect seismic profiles and sidescan sonar swaths from the R/V Bjarni Saemundsson, and the EM300 system on the R/V Arni Fridriksson to collect swath bathymetry and backscatter data. The aim of this survey is to get a comprehensive look at the evolution of the volcanic history of the area. An area named "Stora Hraun" or Big Lava located just southeast of Surtsey Island revealed three major volcanic tuff cones at the depth of some 75 meters below sea level. The largest of these tuff cones has a diameter of 1 km while the two others range in diameter from 400 to 500 meters. Based on their low erosion state we estimate that palagonitisation took place before these craters were subject to erosion. Compared to the erosion state of the two parasitic cones formed in the Surtsey eruption 1963-1967, we suggest that the craters at Stora Hraun were fully palagonised at sub aerial conditions prior to being submerged. This suggests a substantially lower sea level during the Pleistocene.
DE: 3040 Plate tectonics (8150, 8155, 8157, 8158)
DE: 4556 Sea level variations
DE: 8150 Plate boundary--general (3040)
DE: 8400 VOLCANOLOGY
DE: 8414 Eruption mechanisms
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting