When I was thirteen I visited the coastal Alaskan town of Yakutat for a photography trip with my dad. On the beach there were signs to look out for wash up items on the beach from the 2011 Japan tsunami, some of the items included dolls, soccer balls and a lot of trash. I was shocked to see these items on a beach in Alaska when the tsunami occurred over 4000 miles away. This was my first and only experience with a tsunami. Six years later I came here to Greece and learned about the tsunami from the Minoan eruption and my curiosity was piqued again.
It is known that there was a tsunami generated by the Minoan eruption in 1613 B.C from the seawater intruding on the coasts of Crete and Turkey that left a deposit of evidence behind. The evidence includes sand deposits in Crete (120 km away) and western Turkey (200 km away). The wave that hit the west coast of Turkey and the north coast of Crete is thought to have a wave height of 5 meters or greater.
Scientists know that there was a tsunami from the Minoan eruption and it is not questioned. What is questioned and constantly researched is the cause of it, which is still not completely certain.
For many years, the tsunami has been thought to be from the caldera collapse in the last phase of the eruption ever since the research on it begun. It is known that the tsunamis produced by caldera collapse are well documented from historic eruptions.
In a report from 2000 by McCoy and Heiken, it is said that there is an estimate of a 50-meter wave near Thera (the main island of Santorini) which generates open water waves heights between 1.9m and 17m. Velocities needed to propagate a wave of that size had to be high, which shows that the generation of the tsunami must have been from caldera collapse. Figure 1 shows how the collapse of a volcano can cause a large displacement of water then generating a tsunami, which is thought to be how the Minoan tsunami was generated.
It can easily be thought to have been created from caldera collapse because Santorini is a volcano surrounded by water on all sides. The amount of material that was collapsed into a caldera was easily enough to create a tsunami.
Up until 2016, the caldera collapse was thought to have caused the tsunami and that was the only interpretation of the event. The new theory says that the tsunami was produced by pyroclastic flows.
A previous example of a pyroclastic flow producing tsunami is the 1883 tsunami and eruption of Krakatoa. When Krakatoa erupted it was followed by a tsunami that crossed the ocean over 7,000 km away, destroying hundreds of villages in its path. The Krakatoa tsunami was caused by massive pyroclastic flows entering the water and displacing large volumes of water generating a tsunami
The recent theory about the cause of the Minoan tsunami just came out last year by Evi Nomikou. The new interpretation says that the NW breach between the islands of Therasia and Thera was closed off during the main phases of the eruption. It was closed off by tuffs (volcanic material) from phase 3 pyroclastic flows which essentially built a wall around the vent, protecting it from the water.
The caldera was then cut off from the sea during phase 4 which included hot pyroclastic flows that flowed across the island. The wall that was built by phase 3 first broke in the NW causing an inflow of water which flooded the caldera. The inflow of water did not occur until after the eruption finished and filled the caldera with water within a few days.
The tsunami was likely from pyroclastic flows during phases 3 and 4. Nomikou concludes that the tsunami was generated from pyroclastic flows entering the seaward slopes of the island. Combined with the slumping of submarine pyroclastic material. The interpretation is valid with the work done with the 1883 Krakatau tsunami caused by pyroclastic flow.
Hopefully, research will continue to figure out exactly how the tsunami was generated, and this new interpretation is bringing in loads of new information to the topic that will be thought about by many people. Some people may not agree with interpretations and that will continue to be a struggle with science and it will always be that way. If I have learned one thing about science growing up in the U.S. it is that science is constantly not being agreed upon, and there will always be disagreement.
The tsunami was thought to be from the collapse of the caldera because the volcano is surrounded by water on all sides and the force of the collapse was enough to produce a tsunami. It is now thought to have been from the enterting of pyroclastic flows to the water. Those are the two theories of how the tsunami was created.
My first experience with a tsunami was from the secondary impacts from the Japan tsunami and seeing how a tsunami can affect places an ocean away. Now here I am in Greece, seeing where a tsunami started but not seeing where it crossed the sea and left evidence. I hope to one day go to Turkey and see the tsunami from another view point as I did before.
McCoy, Floyd W., and Grant Heiken. “Tsunami Generated by the Late Bronze Age Eruption of Thera (Santorini), Greece.” Pure and Applied Geophysics (2000)
Minoura, K. Discovery of Minoan Tsunami Deposits. N.p., 2000.
Nomikou, P. et al. Post-eruptive flooding of Santorini caldera and implications for tsunami generation. Nat. Commun. 7, 13332 doi: 10.1038/ncomms13332 (2016)