Gavdos Island, a Lifted and Tilted Aegean Crustal Block

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Text, photography: Annemieke van Roekel, geoscience journalist
More articles: www.vuurberg.nl.

Shelter behind the steep southern coast
On historical maps we come across Gavdos in various shapes and names. Gavdos is mentioned in the Bible (Acts 27). The Apostle Paul anchored his ship there to escape the infamous winter storm of Eurakylon when, on his way to Rome, he was unable to reach the ancient port of Phoenix in south-western Crete. Fik Meijer, Professor Emeritus of Ancient History at the University of Amsterdam, describes Paul's voyages (Meijer, 2012): "Despite the storm, the captain had managed to find temporary shelter on a high coast. In the manuscripts, this island is called C(l)auda or K(l)auda. Its southern coast rises more than 300 meters high and its slopes head northwards. A good place to find shelter from the harsh northern winds."

Horsts and graben
Both Crete and Gavdos are made up of a collection of horsts and grabens, geological structures indicating tensional forces and crustal stretching. The seafloor separating the two islands, at depths of more than 1 km, is also composed of such blocks. Strike-slip and reverse faults, a result of compression, have been present here since the Pleistocene. The area is still seismically active due to ongoing subduction.

"The tilting of the 'Gavdos block', which resulted in the characteristic shape of the island, must have taken place around 11 million years ago," explains Jan Willem Zachariasse, geologist / micropaleontologist at the Department of Geosciences at Utrecht University in the Netherlands. "Because of this tilt, the older Pindos rocks, which form the base of Gavdos, are visible all along the southern side"."

 
Fig. 3 and 4. Tilted Pindos limestone (so-called nappes) on Lakoudi Beach. Photo's: A. van Roekel.