Olous EarthCache

Olous

Olous or Olus is an ancient (Minoan), sunken city located near the present day town of Elounda on the western part of the bay of Mirabello on the isthmus of the Spinalonga peninsula. Except of a basilica with splendid mosaics from the 5th century A.D. the remains of Olous are under water.

History

In the Hellenic period a considerable prosperity developed in Olous, due not least to its double harbour, with correspondingly growing political significance. By means of a treaty with Rhodes (probably in 201/200 B.C.) Olous became its dependency. Alliances were also concluded with various Cretan cities, primarily with Lato and Lyttus. Ancient writers recorded that Olous had a population of over 40000 inhabitants.

The governmental system of Olous was a type of democracy. Olous used to have its own currency, most of the coins depicting Vritomartis Artemis on the one side and Zeus as an eagle, dolphin or star on the other. The Oloudians worshiped the gods Tallaios, Zeus, Apollo, Vritomartis and Hesculapius who had saved the town from an unknown disease.

Due to the eastern end of Crete sinking, Olous is now submerged with only a few walls visible above the sea. When snorkeling through, a number of wall bases of houses can be seen together with the old harbour wall.

Many ancient artefacts and inscriptions found at the archeological site of Olous are on display in the archeological museum of Agios Nikolaos.

Geology

The island of Crete is located in one of the seismically most active areas in the whole Mediterranean namely where the northward drifting African Plate moves under the Aegean Plate. It is called the Hellenic subduction zone.
Subduction zones involve an oceanic plate sliding beneath a continental plate and are often noted for their high rates of volcanism and earthquakes. The down-going slab - the leading edge of the subducting plate - is overridden by the leading edge of the other plate. The slab sinks at an angle of approximately 25 to 45 degrees to the surface of the earth.
Rates of subduction are typically measured in centimetres per year, with the average rate of convergence being approximately 2 to 8 centimetres per year (about the rate a fingernail grows). The rate of convergence of the Hellenic subduction zone is about 4 centimetres per year.

In the Hellenic subduction zone large earthquakes are rare. The eathquake that occurred on July 21st 365 A.D. is supposed to be the largest in historical time. Geologists today estimate the quake to have been 8 on the Richter scale or higher, causing widespread destruction in central and southern Greece, northern Libya, Egypt, Cyprus and Sicily. In Crete, nearly all towns were destroyed. It was followed by a tsunami which devastated the eastern coasts of the Mediterranean, particularly Alexandria and the Nile Delta, killing thousands and hurling ships nearly two miles inland. The tsunami left a deep impression on the late antique mind and numerous writers of the time referred in their work to this event.

At Crete the shifting of the land can be seen on peculiar water-level marks (discolouration of the cliffs). In the southwest of Crete these marks are up to 9 m over sea level and are sinking continuously to the middle of Crete until today sea level. If you go further to the east of Crete the marks go on up to 4 metres under water.

With the help of Radiocarbon dating of fossil algae along the ancient sea level mark on the cliffs geologists found out that about 1600-1800 years ago western Crete was spontaneously lifted while the east part sunk into the sea. That's why ancient sites in the east (like Olous) are under sea-level and ancient ports in the western part of Crete (like Phalasarna) are far away from sea today.
Because of the coincide with the earthquake of 365 it's most likely that these phenomena are linked to each other. Comparable earthquakes haven't occurred since then but are possible at any time.

To log this cache please take a picture of yourself or your GPS in front of the ancient site of Olous (this part is only optional!) and answer the following questions:

1. How long is the part of the wall that is visible above the water and is running parallel to the dam? (track log via GPS may help!)
2. What evidence do we have that a landshifting happened at Crete?
3. Which Roman historian described the tsunami that hit Alexandria in 365 A.D. and was caused by the Crete earthquake?

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