Nisyros island is the cone of a dormant, but still ‘active’, volcano laying just south of Kos. Mythology has it that during the war between the Gods and the Giants, Poseidon picked up a large chunk of rock on the island of Kos and threw it at the giant Polivotis as he tried to escape, trapping him beneath it. That rock is the island of Nisyros. Apparently Polivotis is still rather miffed at being trapped beneath Nisyros and all the earthquakes in the area are the result of him struggling to get free.
A more scientific version is that Nisyros lays on the join between the Eurasian and African tectonic plates, as do Stromboli, Etna, Milos and Santorini and is a part of something called the Agean Arch which includes Kos and neignbouring islands. Although the area is still subject to earthquakes the last volcanic activity on Nisyros was a steam eruption in 1888. Today the main crater of St Stefanos just steams quietly to itself.
The island took its present form maybe 150,000 years ago. It is about 8km in diameter and it’s almost 700 metres high and apparently the magma chamber beneath Nisyros is ‘only’ 3 to 4 km deep and is rising!
We visited the caldera on Saturday 30th and had a walk down into the St Stefanos crater. It is perhaps 30 or 40 metres deep and a couple of hundred meters across and appears to be mostly volcanic ash, which sounds hollow when you walk on it. The crater floor is littered with old fumaroles and sulphur deposits and on the eastern side are a line of them still steaming. The smell of sulphur is all pervading and everywhere is streaked with yellow. It is really impressive.