HR: 0800h
AN: OS21A-1519    [Abstracts]
TI: Erosion and submarine canyons on the insular shelf edge south of Iceland
AU: * Kjartansson, E
EM: eik@klaki.net
AF: Marine Research Institute, Skulagata 4, Reykjavik, 101 Iceland
AB: Iceland is surrounded by a clearly defined insular shelf that is usually more than 100 km wide. The depth of the shelf edge is usually between 150 and 300 meters. South of Myrdalur in south Iceland, the shelf is much narrower, around 20 km at the narrowest point. This is probably caused by renewed volcanism in the region during the quaternary. This has caused southward extension of the shoreline and, in combination with quaternary glaciation, a great increase in sediment transported across the shelf. This increase in sediment results in turbidity currents that are strong enough to erode the shelf slope, carving submarine canyons that reach 300 km south of the shelf edge to a depth of 2400 meters in the Iceland Basin. This erosion appears to have removed a few tens of kilometers from the outside of the shelf. The bathymetry of the shelf slope and submarine canyons has been mapped using data that has been recorded using a Simrad EM-300 multibeam sonar onboard the Icelandic research vessel Arni Fridriksson. The morphology of the shelf slope in this region differs from other parts of the Icelandic insular shelf slope. It shows a distinct dendric pattern similar to what is observed onshore where the topography is created by erosion caused by rainfall and its drainage. Two of the submarine canyons originate in the vicinity of two major glacial rivers of the region, Markarfljot and Kudafljot. Reflections from the bottom of these canyons are considerably stronger than from surrounding areas. The third canyon originates near Reynisdjup which coincides with the location of the catastrophic glacial outburst flood that was caused by the eruption of Katla volcano in 1918. The floor of this canyon shows minor contrast in sonar reflection strength, compared to the surrounding ocean bottom. This may indicate that this part of the canyon system is active episodically during floods related to eruptions by Katla. Katla has had significant eruptions approximately every 50 years throughout most of the historical period. A fresh-looking landslide is seen at the shelf edge near Reynisdjup. A direct connection of the submarine canyons to the Maury channel further south and east in the Iceland Basin has not been found yet.
DE: 3002 Continental shelf and slope processes (4219)
DE: 3022 Marine sediments: processes and transport
DE: 3070 Submarine landslides
SC: Ocean Sciences [OS]
MN: Fall Meeting 2005