The lavadome of Methana
About 273 BC (about the exact date there are discussions, one speaks of 230 BC or 270 BC) a gap opened up on the mountain slope of northwest methana, from which sulfur dioxide gas and ash swelled first. Soon, a viscid dacitic lava emerged and built a dome that reached a height of 411.5 m over a period of months.
At this central lava dome a series of gaps broke up, and a stream of molten rock blocks and lava flowed down to 1.5 km in length towards the sea. Like a bulldozer, the rock pushed forward, and eventually, at the end of the activity, a crack split out again at the southern foot of the lava, from which lava flowed out for the last time. It is situated at the today village of Kameni Chora. When the activity was over and the magma chamber was empty, the dugout collapsed and a pseudocrater emerged. Rudolf von Leyden explains the phenomenon of the primary and secondary lavas in his book and also he described the mechanical processes of pressing the lava between primary lava blocks and how the central peak area has formed.
This volcanic eruption was visible until ancient Athens and so there were reports of the ancient writers Ovid and Strabon. There were surely first visitors, too, because the near shrine of Troezen, destroyed by earthquakes as a result of the volcanic eruption, attracted many Athenians. At that time, there were also hot springs at Methana, and as a result of the volcano, which later on, around 180 AD, awas also being described by the Roman travel writer Pausanias.
Lavadomes, such as those in Kameni Chora, are very common on the Methana peninsula and there are still much larger ones, such as the lava dome of Kypseli.
Is the volcanic acitivty ended on Methana?
If you climb the cold lava masses and admire the vegetation with trees and herbs, you quickly think that the volcanism is extinguished here.
However, as Africa continues to fall under the little Asian and European plates, the process of subduction and the associated fusion of North African rocks will continue. This roller of fresh magma will also add new magmas to Greek volcanoes in the future.
Even if there are no eruptions in our lifetime, this does not mean that the volcanism on Methana has been extinguished forever.
It only needs new magma to the already existing magma chambers under Methana, and there are mixing processes that allow gas to free up, then lighter magma is allowed to rise. If there are still tectonic processes (earthquakes!), A new volcanic eruption is possible at any time!
Even today, the gas exhausts in the Bay of Thiafi (and in other places of the peninsula!), the thermal springs and weak earthquakes show that volcanism is only in a resting phase.
Even at the "Weekend of the volcanism of Methana" in August 2013, we discussed the fact that it is very important that Methana gets its own seismographs and also the other parameters (gases, temperatures, elevations and the magnetic field) are regularly monitored.
On the island of Montserrat, too, the volcano had rested since the time of human thought, and then it was suddenly set off and the main town had to be abandoned. Even today the lava dome is active and its pyroclastic streams have made the main town of Plymouth uninhabitable.
Recent research results (for example, by Dr. Ingrid Smet) show that there were much larger and more dangerous phreatic eruptionss on Methana in its geological past and even a caldera was existing.