Text Box:  On 30th December 2002 in the Eolian island, Stromboli, the volcanic activity has led to a giant sea wave approximately 20m high. The wave, technically known as tsunami, was generated by landslides of lava layers in the eastern area known as ‘Sciara del Fuoco’, on impact with the sea. Most probably the lava that erupted two days before, increased the load on the steep slopes of the volcano, making the whole area unstable and determining the collapse in the sea. Experts from the Istituto Nazionale di Geofisica e Vulcanologia (INGV) in Catania said that there is no evidence of summit explosions, and explained that the collapse was determined by the gravitational instability of the area. This hypothesis is supported by two non-volcanic seismic events at 13:15 and 13:22 local time, recorded by the INGV’s instruments. Measurements done by this institute have estimated that the volume of the first landslide was approximately 600 cubic meters, whilst the second one, which actually generated the wave, was calculated to have a volume of 4 million cubic meters.  


Tsunamis or seismic sea waves are commonly produced by movements of the earth’s crust, which cause a sudden rise or fall in the overlying sea surface. When there is a rise, gravity causes the suddenly elevated water to return to the equilibrium surface level. On the other hand if there is a depression, gravity forces the water column to flow into it. In both cases, waves with extremely long wavelengths (100 or 200 km) are generated and are propagated from the point of seismic disturbance at a speed determined by the ocean’s depth. The height of the tsunami is distributed along its wavelength. When the path of the wave is blocked by a coast or island, it slows, its wavelength decreases and its energy is compressed into a smaller water volume as the depth rapidly decreases. The confinement of energy causes the wave height to build rapidly, and the loss of energy is equally rapid when the wave breaks. This leads to an energetic flooding of the coastal area.


The tsunami in Stromboli has caused major damages in the strombolian inhabited area called Ginostra, and in other areas of the island. It has swept away boats, damaged houses situated along the coast and injured six people. Other minor effects of the giant wave were recorded in the confining Eolian islands. Also a tanker was seriously hit by the wave, causing oil spills. According to the experts from the Civil Protection and INGV this phenomenon won’t be repeating itself shortly.


In the last months several seismic and eruptive activities have been recorded in the Sicily area: the impetuous eruptions of Etna, the earthquakes near Palermo and Ustica, the sea boiling phenomenon near the island of Panarea, and the emergence of the submerged island known as Ferdinandea. Enzo Boschi, director of INGV, has explained to the press that all these events are determined by not well understood geodynamic movements of the African and Eurasian Tectonic Plates. Experts however say that the situation in under control and that no serious events are predicted.


In Malta no special sea level anomalous signal has been observed on the day of the Stromboli event. Sea level observations in Malta are conducted in Mellieha Bay by means of a digital tide gauge operated by the Physical Oceanography Unit of the IOI-Malta Operational Centre within the University of Malta. In Malta the only known recorded tsunami is that associated to the Messina Straits earthquake on 28th December 1908. The earthquake was accompanied by a disastrous tsunami which wiped out all the eastern coast of Sicily, and reached Malta some 55 minutes afterwards. The local newspapers reported exceptional high sea levels in Msida Creek and Marsaxlokk Bay. In Msida, seaside resorts and storage houses were inundated with damage to property and merchandise. In Marsaxlokk the impact must have been stronger and fishing boats were crashed against the quay. The tsunami was accompanied by a strong seiche in the Grand harbour where the sea level gauge recorded sea level fluctuations with a maximum crest-to-trough excursion of 2 feet 11.8 inches (= 0.91m). The seiche persisted until late evening. These sea level registrations constitute the only useful records for this tsunami.


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