Temperamental weather today – 15 min of torrential rain followed by 1/2 hour of sunshine. Then it repeats. What better way of coping with a rainy day than writing another blog.
Half way through the Corinth Canal - have a look at the sediment layers
Always wondered how the Gulf of Corinth was created and why it does not reach to Athens. The isthmus of Corinth is only 6.4 km wide compared to the 105 km of length of the Gulf. The Peloponnese could be an island.
As so many features we will discover during our 4 weeks of sailing from Malta to Athens, the Gulf of Corinth is the work of plate tectonics. The African plate sub-ducts south of Crete and the Peloponnese below the European plate. A good hundred kilometres to the north, the European plate is brittle and cracks. Fault lines develop. Between the Northern and southern fault lines, the downward movement of the African Plate pulls a part of the European Plate downwards. A tectonic graben of 3 km depth opened.
The Gulf of Corinth with the fault lines in red - the Gulf widens by 1 cm/p.a. as of. today
By geological standards, the graben is young. It opened about 2 million years ago. Could not find out why the graben does not extend all the way to the Gulf of Saronikos. Maybe I failed to understand the technical terms used in the geology papers consulted. Knowing that the Canal of Corinth cuts through lime and stand stone sediments, the answer may lie in the higher elasticity of these stone formations. That is at least how it is in the Swiss Alps. Large layers of limestone are bent and twisted to a remarkable degree without breaking. If so, the higher elasticity may have prevented the development of fault lines and no graben opened.
Cut through the Graben Structure of the Guld with the sunken parts
Be it as it may, the ancient Greeks noted the geographical importance of the Isthmus and built the town of Corinth overlooking it. With two lines of communication crossing here (Adriatic to Aegean - Athens to Peloponnese), the place was ideal for commerce. It also had significant strategic importance. The Corinthians used another benefit of the Isthmus’ geology. Just west of its most narrow place, there is a giant limestone block. The Corinthians could thus build both a lower and a well-fortified upper town. Acrocorinth is an even more impressive fortress than the Acropolis in Athens.
Walls and entrance to Acrocorinth - modern Corinth is visible on the shore of the Gulf
The narrow land-bridge also inspired Greek and Roman leaders to develop schemes which would allow ships to cross the Isthmus. In the 7th century BC, the Corinthian Tyrant Periander started the construction of the Diolkos on which ships could be pulled over the Isthmus.
Possible route of the Diolkos - there is some dispute over it - much evidence disappeared
How ships might have been pulled on an 8 wheel trolley over the Diolkos
Emperor Nero tried to build a canal with slaves taken during the Jewish rebellion but the effort exceeded the manpower available. It was not the lack of expertise in engineering – we have seen in Seleucia Pieria in 2018 (Blog B +15) how the Romans diverted an entire river through a 400m long tunnel they chiseled. But the plans came to naught and posteriority was not nice to Nero’s grandiose plans. His Villa Aurea made place for the Colosseum, his canal construction site decayed over the centuries.
Most of Nero's ruins had to be destroyed when the new canal was build on the same site
It was only in the late 19th century that the idea of digging a canal through the Isthmus was taken up again and by 1893 it was done. The canal is so narrow that the walls continued to collapse and extensive repair was needed for several decades. Today, the canal is safe. Human beings completed what plate tectonic had not done – Athens now had direct access to the Adriatic.
Entering the Canal from the North - can’t wait to cross it – not done it before – only stood on the bridge crossing. To the right are a few remains of the 2'700 year old Diolkos
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