Thursday 26 January 2012

Dodecanese Islands and Crete shaken by Earthquake.

At approximately 6.25 am local time (4.25 am GMT) on Thursday 26 January 2012 an Earthquake in the Aegean Sea to the north of Crete and west of the Dodecanese Islands was felt in both areas. The Quake was recorded by the Hellenic Unified Seismological Network as measuring 5.3 on the Richter Scale and occurring at a depth of 30 km, and by the United States Geological Survey as measuring 5.2 on the Richter Scale and occurring at a depth of 18 km. The quake has been followed by a series of aftershocks, some of which have exceeded magnitude 4.0 on the Richter Scale. Neither the original quake nor the aftershocks are reported to have caused any significant damage, nor casualties

Map showing the location of the main quake, from the United States Geological Survey. Pink line south of Crete is the boundary between the Aegean Sea Plate and the African Plate.

Crete is located on the southern edge of the Aegean Sea Plate, a small tectonic plate being forced southwest by the eastward motion of the Anatolian Plate, which underlies Turkey. Immediately to the south the African Plate is moving northward, creating a convergent margin. The African Plate is being subducted beneath the Aegean Plate in the Hellenic Trench, passing under Crete and the Aegean. This is not a smooth process, the rocks stick to one-another, then periodically move suddenly when the pressure becomes to great, causing Earthquakes.

Diagram showing the subduction of the African Plate (left) under Crete (right).

The subduction zone also leads to volcanism in the Dodecanese, as rocks from the African Plate are melted by the heat of the Earth's interior and rise up through the overlying Aegean Sea Plate, forming the volcanoes of Gyali, Santorini, and Nysiros, as well as a number of submarine volcanoes. This has lead to some catastrophic incidents in the past, most notably the destruction of the ancient Minoan civilization of Crete by a tsunami triggered by an explosion in the Santorini Caldera.

An artist's impression of a Minoan city being inundated by the Santorini Tsunami.

Earthquakes have also taken their toll on life in the Aegean over the millennia, and are a more regular threat. Earthquakes on Crete have three times (365 AD, 1303 and 1810) caused tsunamis that have led to devastation on the Egyptian Coast. On the Boundary with the Eurasian Plate the cities of Sparta, Corinth and Athens have all been devastated by Earthquakes on various occasions, as has Rhodes, on the boundary with the Anatolian Plate, most famously in 226 BC, when a quake destroyed the famous Colossus, a giant statue that stood at the entrance to the harbor.

See also Earthquake in the Gulf of Corinth, and Earthquakes on Sciency Thoughts YouTube.