Countdown to Disaster, but When?

The 1613 +/-13 BC Minoan eruption is known worldwide for its colossal eruption that was nearly equal to the eruptions of Tambora and Krakatau in Indonesia. We are studying this specific eruption because while it greatly effected the morphology of Santorini, the population of the island was effected as well (1). This eruption is crucial in our understanding of future caldera eruptions and expands our knowledge of the likelihood of another eruption.


The Minoan eruption had four distinct eruption phases with 7 centimeter ash warning layer at Akrotiri. (1). We have seen the warning layer in our field work at many locations on the island Including Ancient Akrotiri. The eruption style of this caldera was ultra-plinian, meaning that it is of the highest explosivity including different types of pyroclastic flows and surges.

The first phase of the eruption is marked by pumice fall. The second phase was the surge, which is recognized at various locations where we have observed the fall. The locations of Fira Quarry, Cape Plaka, Vichada Beach and Caldera beach on southern Thera all have evidence of the second phase? The third phase, which came from a cool and wet pyroclastic flow, is present just south if Fira where we are living.It contains enormous blocks and bombs making it easy to recognize. The fourth phase was a hot pyroclastic flow, rich in lithic fragments. (2).

Pots preserved from the pumice fall from the first phase of the eruption.
Pots preserved from the pumice fall from the first phase of the eruption.

These various phases of the eruption are important to expand our knowledge of the eruption. While not only geologists find the volcanic history important, it is useful information as general knowledge to be aware of your surroundings. I say this because not only have we been told continuously to be aware of our environment, but it is applicable to daily life as well. Being spatially aware is crucial in our lives here on Santorini because it can be very dangerous where you place your towel on a beach. We wouldn’t want to lay under a towering cliff with loose cinders because it’s dangerous and Lisa would not be thrilled. All this information is exciting to learn because wouldn’t you want to be to know when the next Minoan eruption could happen?

Here I am posing for a picture, to prove that was actually at Ancient Akrotiri. I was amazed at how advanced the Minoan people were for their time.
Here I am posing for a picture, to prove that was actually at Ancient Akrotiri. I was amazed at how advanced the Minoan people were for their time.

The past is key to helping forecast the future, especially in geological terms. The way we are able to know how often caldera eruptions occur globally is with two methods. The first used geological record of the past 200 years of eruptions while the other by using the distribution, size, and geological history of large caldera eruptions (3). A VEI, volcanic explosivity index, measures and ranks the height of eruption column and qualitative observations to help determine the explosivity.

The Minoan eruption was initially said to have had a VEI of 6, but was recently debated saying it could be closer to 7.1, suggesting it was much stronger than when it was first researched.

Imagine looking out your window when suddenly an earthquake strikes and you see the center of a volcano with an eruption column roughly 36 kilometers into the air. It could happen midday but the sky would be dark, raining pumice and ash. That’s what a VEI 7.1 would look like.

Four phases of the caldera forming, showing the drastic landscape changes during at a caldera.
Four phases of Caldera evolution, showing drastic landscaped changes.

The current knowledge and records of past eruptions tells us that Minoan size eruptions are rare but still very real. Within geology there are always interpretations being made, and one article by R.W. Decker presents data that suggests the average recurrence interval for equal to or exceeding VEI 8 is 50,000 years (3). Imagining a volcano eject 30 cubic kilometers of pumic and ash is astonishing, thankfully Minoan sized eruptions don’t happen everyday. So we’re safe… at least for now.

 

(1)Friedrich, W.L., 2009, Santorini: Volcano, Natural History and Mythology, Denmark: Aaruh University Press, 81 P.
(2)Druitt, T.H. 2014, New insights into the initiation and venting of the Bronze-Age eruption of Santorini (Greece), from component analysis. Bull Volcanology, 76:794
(3)Decker, R.W., 1990, How often does a Minoan Eruption Occur? In Thera and Aegean World.

 

 

 

 

 

 

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5 thoughts on “Countdown to Disaster, but When?”

  1. Two questions…..1) What is Mount St. Helen’s last eruption categorized as? 2) If the magma lake under Yellowstone blows, would it be a minoan sized eruption?

  2. Nice mention of being spacially aware… Wouldnt want to be found under a talus cone at the beach! I also enjoy that map, its a very nice representation of the phases and is very helpful with what everything looked like throughout the four phases.

  3. Your depth of knowledge and understanding is coming along well! There is a typo in the 3rd sentence of the 3rd paragraph…what looks like a ? out of place. A small correction on the phases (phases 2 and 3 contain blocks with 2 containing most block sags). Phase 4 is composed of both hot and cold pyroclastic flows depending on your location on the island.

    Be careful of extraneous words like “I say this because” and “not only.” You can leave these out as they take away from the main points you are trying to get across.

    I like your map of Santorini showing the evolution of the landscape. The word “phases” in the figure caption suggests Minoan phases, but these maps actually show the 4 calderas that have formed in the last 200,000 years.

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