along the Terceira Rift. From the beginning of the islands' settlement, around the 15th century, there have been about 30 volcanic eruptions (terrestrial and submarine) as well as numerous, powerful earthquakes. The island of São Miguel in the Azores is the site of the Sete Cidades volcano and caldera, which are the byproducts of historical volcanic activity in the Azores. The submerged island of Spartel near the Strait of Gibraltar has also been suggested. In Europe Several hypotheses place the sunken island in northern Europe, including Doggerland in the North Sea, and Sweden (by Olof Rudbeck in Atland, 1672–1702). Doggerland, as well as Viking Bergen Island, is thought to have been flooded by a megatsunami following the Storegga Slide of c. 6100 BC. Some have proposed the Celtic Shelf as a possible location, and that there is a link to Ireland. In 2004, Swedish physiographist Ulf Erlingsson proposed that the legend of Atlantis was based on Stone Age Ireland. He later stated that he does not believe that Atlantis ever existed but maintained that his hypothesis that its description matches Ireland's geography has a 99.8% probability. The director of the National Museum of Ireland commented that there was no archaeology supporting this. In 2011, a team, working on a documentary for the National Geographic Channel, led by Professor Richard Freund from the University of Hartford, claimed to have found possible evidence of Atlantis in southwestern Andalusia. The team identified its possible location within the marshlands of the Doñana National Park, in the area that once was the Lacus Ligustinus, between the Huelva, Cádiz, and Seville provinces, and they speculated that Atlantis had been destroyed by a tsunami, extrapolating results from a previous study by Spanish researchers, published four years earlier. Spanish scientists have dismissed Freund's speculations, claiming that he sensationalised their work. The anthropologist Juan Villarías-Robles, who works with the Spanish National Research Council, said, "Richard Freund was a newcomer to our project and appeared to be involved in his own very controversial issue concerning King Solomon's search for ivory and gold in Tartessos, the well documented settlement in the Doñana area established in the first millennium BC", and described Freund's claims as "fanciful". A similar theory had previously been put forward by a German researcher, Rainer W. Kühne, that is based only on satellite imagery and places Atlantis in the Marismas de Hinojos, north of the city of Cádiz.