Sometimes there is news about volcanoes that get blown out of all proportion. The island volcano of Santorini has unassumingly been erupting with small eruptions for the last 2 000 years or so. It is though mainly known for its VEI-7 Thera eruption 3 600 years ago.
Why do I mention the small ones? Well, a large volcano takes a lot of time to recuperate after a large eruption. First we need to understand what the large eruption was and what it did to the plumbing of the volcano. The Thera eruption started as a very large normal eruption that emptied out the magma chamber at rapid pace. In the end the roof of the chamber fell in on itself and water poured in. That in turn caused a very large steam explosion blowing away a sizeable chunk of the Island. One should remember that this is by far not the largest such eruption of Santorini, but thing is that they are far apart.
The effect of the collapse and the subsequent hydro magmatic explosion is that it left the volcano without a magma chamber. Where the chamber used to be there was only rubble. For the first 1 600 years after the eruption there was not even a chance for even a small normal eruption, any magma pushing up was deposited straight into the water filled rubble. In the end a solid roof started to build, and the cycle turned into the pattern we have today of small island building eruptions. Those eruptions are centered on the Nea Kameni Island with a few exceptions.
A few days ago Nature Geoscience published a paper on the current activity at Santorini. The paper itself was rather factual. Nea Kameni uplifted 14 centimeters from January 2011 to April 2012. That equals to 10 to 20 million cubic meters of magma. Sounds like a lot of magma does it not? We are after all talking about one of the largest active volcanoes around.
Well, the worlds combined press services though it was a lot. They picked up on it with war headlines.
Now let us look at it critically. The Italian volcano of Campi Flegrei inflated a bit in the 70s. It did 270 centimeters in less than half the time of Santorinis 14 centimeters without showing any other signs of erupting. After inflating 270 centimeters it went back to sleep, goes to show that it takes quite a lot for a supervolcano to go super if nothing else.
Now back to the magma chamber at Santorini and its size. The reason for Santorini having small and slow VEI-2s and a couple of VEI-3s and nothing bigger is that the chamber is still too small and weak to be able to withstand the pressure and volumes of a large eruption.
So, how about all that magma, it must be dangerous? No, not at all. Why? Because it is only 0,01 to 0,02 cubic kilometers of magma. If all of that jumped out of the volcano in one good eruption we are talking about a small VEI-3. Only problem is that all of it will not come up. Normally only one tenth to one twentieth of the magma comes to the surface from the chamber during an eruption. Bummer for all those who dream about gloom and doom.
So, taking that fact into account we are looking for 0,0005 to 0,002 cubic kilometers of lava coming out of the volcano. That is a midsized VEI-1 to a small VEI-2. Quite normal for Santorini really, the island has had a lot of them.
Gosh darn, who stole my end of civilization?