Underwater volcano discovered off Sicily

The find was the result of investigations into a submerged volcanic cone which caused an international rumpus in the summer of 1831 when, after an earthquake on the Sicilian coast and much spitting of fire and stones from below the sea, it rose above the surface of the waves. The new island was claimed by the British, who sailed over from Malta, planted the Union Jack and named it Graham Island.

An island at this strategic point in the Mediterranean - closer to the southern coast of France and Spain than Malta - was of obvious interest to the world's greatest naval power. But Ferdinand II, the Bourbon king of the Kingdom of the Two Sicilies, saw the matter differently and sent men across to the smoking, evil-smelling cone to remove the flag and plant one of his own. He named the island Ferdinandea.

The French duly joined in, sending a geologist and calling it Giulia after the month in which it made its appearance. The Spanish also showed an interest, but before a shot could be fired over its ownership, Graham/Ferdinandea sank back beneath the waves.

That is where it remains, outside Italy's territorial waters and, being only seven metres below the surface, a menace to shipping. But the injury to Sicily's pride still rankles. In 2001 in an attempt to forestall future arguments, Domenico Caluso, a doctor in the nearby town of Sciacca, persuaded Ferdinand's descendant, who styles himself Prince Carlos of Calabria, to sponsor a permanent nameplate. A marble plaque weighing 150kg and inscribed "This piece of land, once Ferdinandea, belonged and shall always belong to the Sicilian people" was ceremonially lowered on to Ferdinandea in March 2001, but within six months it had been broken into 12 pieces. The culprit remains a mystery.

The dispute over Ferdinandea has now been overshadowed by the discovery that the former island is just one outcrop of a far grander volcano, the largest seamount (underwater mountain) off the Italian coast, and one that is still active, though for now emitting only gas. Professor Giovanni Lanzafame, of Italy's National Institute of Geophysics and Vulcanology, named the volcano Empedocles, after the pre-Socratic Greek philosopher who lived in Sicily and plunged headfirst into the crater of Mount Etna, still highly active today, in the interests of scientific research.

Professor Lanzafame said: "Thanks to sonar readings and the use of robotics, we were able to extend our inquiry over a much larger area and discovered that Ferdinandea and other nearby submarine banks with names such as 'Terribile' and 'Nerita' are no more than the accessory cones of a much vaster volcanic structure in the form of a horseshoe. It measures 25km by 30km at the base, and is thus comparable in size to Etna - though it is smaller than Etna in height, extending only 500m above the sea bottom."

He and his colleagues believe Empedocles was created millions of years ago when, as a result of the collision of Africa and Europe, deep fractures opened up which were the origin of the Sicily Canal, causing magma to rise to the surface and the formation of a underwater volcanoes.

Enzo Boschi, president of the Italy's Geophysics and Vulcanology Institute, said: "The idea that there was a much larger volcanic structure in this zone has been around as a working hypothesis, but the underwater exploration done in the course of this campaign makes it more concrete."

The scientists believe there is no imminent risk of eruption, nor of the appearance of new islands.