Santorini Earthquakes Create Panic In Greece As Locals Fear Volcano Could Erupt

The Greek Island of Santorini is in the headlines again, not because of the massive increase in tourism and cruise ships last season, but because of a swarm of severe earthquakes this week. With growing concerns about the Kolumbo submarine volcano, 11,000 locals and visitors have recently departed the island, and many are wondering whether the earthquakes could set off a potential eruption or the formation of a new volcano.

Greece’s government declared a state of emergency on Santorini this week, and residents and hotel owners were required to drain all swimming pools, as water movement could destabilize the buildings. People were also instructed to avoid old buildings. Small rockslides happened along the cliffs, prompting Greek authorities to restrict access to areas identified as high risk. Discussions about evacuation plans have begun among Greek authorities as residents are becoming increasingly afraid.

Scientists and researchers remain confident that the volcano will not pose a threat despite a report published in Geochemistry, Geophysics, Geosystems revealing that a previously undetected magma chamber is growing beneath the Kolumbo volcano that could lead to another eruption.

According to a National Institute of Geophysics and Volcanology report, “The affected area is one of the most seismically active in the Hellenic volcanic arc region. The current events occur along the Santorini-Amorgos fault zone, known for its ability to generate high-magnitude earthquakes. The most destructive earthquake recorded in the area occurred on July 9, 1956, with magnitude 7.1, followed by a strong aftershock of magnitude 6.9, causing widespread damage and a violent tsunami.”

Recent geological studies have also highlighted a fault with a recently exposed surface at the base of the seafloor, compatible with the 1956 earthquake. “The combination of active tectonics and the presence of submarine faults implies a significant risk of earthquakes of great magnitude, with potential impacts on coastal communities and local infrastructures. The possibility of secondary phenomena, such as tsunamis or seabed instability with associated submarine landslides and earthquake-induced landslides on the surface, represents an additional vulnerability for the region. At present, landslides have already been reported in Santorini that have required the intervention of the civil protection authorities,” the report added.

Kolumbo Volcano Is Restless

Located on the northeast side of Santorini, the Kolumbo submarine volcano experienced a major eruption in 1650. This eruption resulted in the formation of a new island, with lava flows extending towards the Santorini coast. The 1650 eruption ejected ash as far away as Turkey and produced pyroclastic flows that led to the deaths of about 70 people on Santorini, along with a large number of livestock due to toxic gases. Additionally, a tsunami likely occurred during the collapse of the volcanic cone, causing damage to nearby islands and flooding the flat coastal areas, on the eastern side of Santorini, where ruins from Roman times were uncovered.

Historic eruptions of Santorini formed new islands within the caldera during the Minoan eruption. In 2011-2012, Santorini went through a phase of unrest, with increased seismic activity, ground deformations, and gas emission changes from Nea Kameni’s fumaroles.

Greek Prime Minister Mitsotakis addressed the nation this week following the strongest quake, urging calm while emphasizing that all necessary precautions were being taken to protect residents and visitors alike. The Greek Tourism Ministry is now planning a response to address the impact of tourism on the islands surrounding Santorini, including Amorgos, Ios, Naxos, and Anafi.

I spoke with Michele Paulatto, an Advanced Research Fellow in Volcano Geophysics who offered more details on the earthquake and volcano risks. “The current activity is located on a set of faults that extend between Santorini and Amorgos. The largest events in the sequence have had a magnitude of 5.2. The main concern regarding hazards is the possibility of larger earthquakes. There is a lot of debate in the community on whether a larger earthquake will follow. The worst-case scenario is a repeat of the 1956 Amorgos earthquake, which had a magnitude of 7.8, the largest earthquake in Europe in the last century. This is a possibility, but it is hard to tell how likely it is.”

“For the moment, it seems unlikely that the activity would reach such high levels,” he added. “The current events are not exactly on the fault that slipped in 1956 but are on a nearby fault and seem to be more restricted in geographic extent. The likely scenario is that the maximum magnitudes will remain around 5.0, and the activity will slowly subside over a few weeks. Nobody can predict what will happen; we can only analyze possible scenarios and prepare as best as we can. Special measures and caution are certainly warranted.”

Regarding the risk of another volcanic eruption, Paulatto adds, “There has been some slight increase in activity at Kolumbo volcano and Santorini volcano, enough to warrant close inspection, but not enough to raise the volcanic alert level. Earthquakes can trigger eruptions, but I am unaware of that happening at Kolumbo or Santorini. The earthquakes have mostly been away from the volcanoes. If we see an increase in earthquake activity directly under the volcanoes, the likelihood of an eruption will increase. This is closely monitored with the existing seismometer network, and some additional seismometers have been deployed.”

If there starts to become an increase in earthquake activity, Paulatto says, “It is important to keep in mind that seismic crises at volcanoes don’t always lead to an eruption. See, for example, what happened in 2011 on Santorini when there was a seismic swarm, ground deformation, and increased gas emissions on Nea Kamini, but no eruption followed. Again, monitoring is key. Not just the earthquakes but also ground deformation and gas emissions.”

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Santorini earthquakes