MercoPress. South Atlantic News Agency

South Sandwich Islands are the emergent tips of huge volcanoes, according to BAS

Bathymetric map showing submarine volcanoes around Zavodovski Island and numerous seamounts and sediment waves in the foreground (Image BAS)

Earlier this year, geologists on the British Antarctic Survey (BAS) ship “RRS James Clark Ross” completed a project to map the sea floor around the volcanic South Sandwich Islands using multi-beam sonar. This completes a project started three years ago, reports the latest edition of the South Georgia newsletter.

The islands are rich in marine life, but also are sources of poorly quantified hazards from volcanic eruptions and tsunamis generated by land-sliding of submarine parts of the volcanoes.

The 30m resolution survey showed for the first time that the South Sandwich Islands are the emergent tips of huge volcanoes that rise from seafloor about 3 kilometres deep. Scattered among these large volcanoes are about 20 smaller, submarine volcanoes known as seamounts, some of which rise to within 100m of the surface. These are likely to be biological hotspots, especially as several are likely to be releasing volcanic hot springs onto the sea floor.

The risk of land-sliding of the volcanoes to form tsunami is less than might be anticipated. Although sizeable landslides clearly have occurred, they are infrequent. This is because slope gradients have been reduced by build-up of thick piles of sediments on the lower slopes.

BAS scientists Phil Leat, Tara Deen and Alex Tate carried out the survey from January to March 2010 with scientists from the Aon Benfield Hazard Research Centre of University College London led by Simon Day.