You know how sometimes people will refer to a serious or dire situation as Defcon 5, or even 6 if they’re really dramatic? Well recently when I was watching the 1983 film War Games, I learned that Defcon 5 is actually the least severe alert and Defcon 1 is the most. For the Minoans, phase 0 would have been Defcon 0. Now I’m being dramatic, but not that much because phase 0, amongst a few other signs, warned the Minoans that if they did not leave Ancient Akroteri they would all perish in the massive explosion of the caldera.
The Minoans didn’t have to be scientists to read the signs the island was giving them. The final straw, Defcon 0, was phase 0 of the eruption. Phase 0 was a small eruption of the volcano. Some geologists might refer to an event like this as a throat-clearing event. This event deposited up to eight centimeters or less of ash at various locations around the south side of the island (Fig. 1). This small eruption was like a light drizzle before a gigantic downpour. There’s no doubt that the Minoans experienced this event and made the call that it was time to relocate. For more specifics about phase 0, see Rachel’s blog.
Additionally, the Minoan eruption was no exception to increased seismicity that accompanies impending volcanic activity. Prior to phase 0, the Minoans would have been experiencing more frequent and more intense earthquakes. Evidence of this lies in the ruins at ancient Akrotiri, excavations have revealed broken staircases and debris collected in the streets (Fig. 2). The Minoans had probably just experienced a fairly large earthquake and had cleaned up the wreckage and put it in the streets to be moved when they decided it was time to leave. The Minoans were extremely advanced (they had indoor plumbing!) so it’s likely that they noticed the increase in intensity and frequency of earthquakes and made the decision to head for sturdier ground .
The Minoans knew what was coming for them and they tried to leave the island. In Ancient Akroteri, you can actually see signs that the Minoans left. One such example is that they had stacked all of their furniture and moved their storage jars to the edges of the rooms, just like we would do if we were preparing to move (Fig. 3). Additionally, “few valuables have been found in the excavation”, which most likely means that the Minoan people took them with them when they left .
Thus far, no bodies have been found in the excavations of Ancient Akroteri. Human bodies are made of organic material, so they would have decayed in the time since the eruption, but if there had been bodies there they would have left an empty cavity that scientists could make molds of. This is what happened at the Mt. Vesuvius eruption in 79 A.D. Ash emitted from the explosion perfectly preserved the entire city at its state at the time of the eruption. Based on this, we can assume that the Minoans escaped from the island by boat. However, Ancient Akroteri has not been fully excavated, so there is a possibility that their bodies could still be there.
Had the Minoans stuck around, they would have been subject to one of the most violent and catastrophic eruptions of all time. The volcano had four more phases of eruption following phase 0, each new phase more explosive than the last. Phase 1 of the eruption would have been enough to kill their entire civilization. The first phase consisted of at least five and a half meters of ash and pumice raining down over the entire surface of the island. That was followed by phase 2 – turbulent pyroclastic surges, or clouds of expanding gases that move across land and water at 200-300 kilometers per hour at anywhere between 200-300 degrees Celsius, destroying everything in their path. Phase 3 was another round of pyroclastic flows, less turbulent but more dense gas flows, that move across the land and water incinerating everything in their path. The ruins at Ancient Akroteri were only preserved by the thick layer of ash on top of it. Phases 2 and 3 deposited more and more ash on top of that. Finally, phase 4 produced even hotter pyroclastic flows, around 450 degrees Celsius. This doesn’t even mention the volcanic weather, tornadoes, and tsunamis that would have accompanied the collapse of the volcano.
In reality, the Minoans probably did not make it far away enough away in time to escape the effects of the volcano, and almost definitely didn’t get far enough away to escape the tsunamis that ensued. Minoura et al. (2000) did a study that found that the entire eruption happened over the course of approximately 24 hours . It’s extremely unlikely that the Minoans were able to sail far enough away within 24 hours notice to escape safely. I’m an optimist though, so I like to think that they tried to and it makes sense that they heeded the volcanos warning based on the evidence in Ancient Akroteri. Perhaps if they had some of our modern volcano monitoring techniques they could have gotten out earlier.
One of the clearest signs of an impending eruption used by modern volcanologists is an increase in seismic activity, or earthquakes. When a volcano is building up to an eruption there will be an increase in seismicity, the frequency and intensity of earthquakes, over several months, similar to what the Minoans experienced. At active volcano sites, volcanologists monitor networks of seismographs for increases in seismic activity and the locations of the foci of these earthquakes .
Another technique used by geologists is GPS tracking of ground deformation. Using this method, geologists can map what is happening underground in the volcano. Basically, as magma is rising up in the chamber it “pushes the skin of a volcano up and out, like a balloon filling with air”. Very sensitive tiltmeters and tools can measure the slightest changes and indicate to volcanologists what is happening below the surface like how fast the magma is moving, where on the volcano it will erupt, and how deep the magma source is based on the deformation of the ground .
One of the most modern methods of predicting volcanic eruptions is to monitor gas emissions from the vent of the volcano. Leading up to the eruption, a volcano will increase emissions of carbon dioxide (CO2) and sulfuric acid (SO2). These gases are normally liquified within the magma but as the pressure in the volcano decreases for the eruption, they come out of solution and can be measured at the vent of the volcano .
Last but not least, scientists can study the history of volcanoes to learn more about how they will erupt in the future. The history of the volcano tells a story about that volcanoes personality – how long it is dormant between eruptions, how big the eruptions are, and what types of eruptions it has had. Especially on Santorini, the history of the volcano tells us how the volcano behaves. The island has had four caldera forming eruptions in its history, and the deposits from those eruptions can be used to predict what size eruptions this volcano will have and how far out the next eruption would be. More details about the monitoring of volcanoes by modern volcanologists will be posted with next weeks blogs.
Science has made a lot of progress with the predicting of volcanic of activity. I like to think that the Minoans made a valiant effort to escape their doom, but with modern technology they would have had a much better chance of escaping in time.
 Friedrich, Walter F., 2009, Santorini, Narayana Press, pages 83-85.
 Minoura et al., 2000, Discovery of Minoan tsunami deposits, Geology, Vol. 28, No. 1, pages 59-62.
 Tyson, Peter, 1996, Can we predict eruptions?: http://www.pbs.org/wgbh/nova/vesuvius/predict.html (Accessed June 2015).