Measurements taken by satellites indicate that the eastern flank of Mount Etna is slowly sliding into the Ionian Sea. However, these measurements only take into account the portion of the volcano that is above the water surface, as the satellite signals cannot penetrate the water and measure the movements and deformations of the soil underwater.
So scientists in Kiel have set out last Thursday on the research vessel Poseidon to set up a new survey network off the Sicilian coast so as to take measurements for the submerged portion of the volcano.
With seven eruptions since the start of the millennium, Mount Etna in Sicily is the most active volcano in Europe. Its lava flows have repeatedly destroyed houses, roads and the other infrastructure in the vicinity. The town of Catania, located at the foot of Mount Etna, is an important industrial centre in southern Italy with about a million inhabitants. Not surprisingly, the scientists and authorities there monitor the volcano's status very closely. There are stations that use satellite data to accurately detect the movement of the mountain.
And now, the monitoring will be extended with the help of the scientists from GEOMAR. On board Poseidon are monitoring systems similar to those installed in the seabed in earthquake-prone regions like Istanbul and off northern Chile. Project manager Dr Morelia Urlaub (from GEOMAR Helmholtz Centre for Ocean Research Kiel) explained that their systems made use of a sound-based variant which opens up new avenues for research into natural hazards in the oceans.
During this expedition, the researchers will install six geodesic stations at depths of 700 metres below the water surface off the eastern coast of Sicily.
Using sound, the geodesic stations would measure the distance from one another to a fraction of a centimetre. Three ground-inclinometers and six classic ocean bottom seismometers, which can detect even the smallest vibrations underground, complete the monitoring network.
Just a slight movement of the volcano's flanks may signal an impending eruption, and underwater landslides can trigger a tsunami. This would spell danger for the entire region, particularly in the densely populated coasts in the Mediterranean where millions of tourists congregate during the summer months.
"The idea of a tsunami in the Mediterranean is not conjured out of thin air. An earthquake in the Strait of Messina in 1908 triggered a tsunami, killing about two thousand people, "said Professor Krastel in German.
Marine geodesy, the sound-based surveying of the Earth underwater, is still a very new method used in the research of natural hazards. Nevertheless, Dr Urlaub expressed hope that knowledge about the movements of Etna could subsequently be expanded.