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Case Study 15. Greece – How Dormant are the Islands?

ByM. Cooper

Geophysical aspects and history of activity The most famous Greek volcano is Santorini, which last erupted in 1950. Its most devastating recorded eruption was in 1600BC and buried the city of Akroteri, possibly giving rise to the legend of Atlantis. Three islands remained after this eruption – Thera, Therasia and Aspronisi. The Santorini caldera has a diameter of 11km northsouth and 7.5km east-west, with a depth of 390m in the north. The 1950 eruption produced a lava dome, lava flow and explosive activity, while activity was also recorded in 1939-41, 1925-28, 1866-70, 1707-11, 1650, 1570-73, 726, AD46-47 and 197BC (Seach, 2009). Methana, on the Methana Peninsula of the Peloponnese is made up of a series of lava domes, which last erupted in

Risk factors As has been noted elsewhere in this book, in relation to many volcanoes the risk factors for tourism deriving from the Greek volcanoes are latent at present. The most dangerous situation is considered to be Santorini, which has been labelled a decade volcano in order to be closely monitored and researched. However, as stated above, the activity of Nisyros volcano is evident by many hydrothermal vents or fumaroles as well as small boiling springs at the bottom of the crater and this activity attracts the attention of hundreds of visitors daily during the tourist season (Figure CS15.2). Transport to the volcano is usually by organized bus tours, with the approach of the narrow, windy road into the caldera only possible in one direction according to agreed times. Once inside the caldera the crater itself can be accessed via a steep, but potentially unsafe climb downhill, which is made even more difficult

produced phreatic eruptions. Currently fumarolic activity occurs in the caldera, and hot springs are found on the coast. The volcano has erupted at least 13 times during recorded history. A volcanoseismic crisis on Nisyros occurred between 1995 and 1998, and was accompanied by 14cm of ground uplift on the island. More than 1600 seismic events were located within the KosNisyros-Tilos area. Several shallow tectonic earthquakes at depths up to 10km with larger magnitudes up to 5.5 occurred along the fault system between Tilos and Kos. And in January 2003 the crater was declared off limits due to increasing temperatures and growing surface cracks. The temperatures in the hydrothermal system increased from 210oC to 315oC.