Between January 2011 and February 2012, Santorini was enveloped by crisis. An average of 50 earthquakes a day constantly shook the islands and terrified locals. Santorini residents refer to the 14 months of earthquakes as the Crisis Period and were relieved when the seismic activity finally ceased. But what many of the locals didn’t realize was that deep below the surface of the water the caldera floor was sending a message: the volcano is recharging.
The volcanic complex of Santorini has experienced four separate caldera forming eruptions over the past 200,000 years. During these Plinian-style eruptions, the magma chamber is emptied and excavated resulting in the collapse of the dense land which rests above it. Over time, new magma pushes up through the weak crust of the fault lines that cut across the Santorini islands and refill the chambers. When magma rises through the crust, the activity is often accompanied by volcanic tremors (relatively low magnitude earthquakes that originate near the chamber) and ground inflation (literally the surface of the ground rising) as the magma pushes against the sea floor.
During the Santorini crisis period, the sea floor north of Nea Kameni experienced severe inflation; an uplift of 150mm/year. This inflation provides significant insight into the recent activity of the collection of magma chambers that fuel Santorini’s volcanic complex. Although the uplift did cease in February 2012, there have been no signs of deflation (the ground surface returning to its original height). This evidence, along with deeply rooted volcanic tremors, indicates magmatic activity. New magma is rising up towards the caldera, lifting the sea floor and recharging the volcanic complex (1).
So what does this mean for Santorini?
Although we don’t have the technology today to confidently predict the timing or severity of a volcanic eruption, geologists monitoring Nea Kameni have made predictions concerning the next Santorini eruption. According to current data, the probability of another ultra-Plinian eruption, such as the Minoan eruption of 1613 +/- 13 BC that permanently an drastically altered the landscape is 1 in 30,000 (1).
More likely is a small shield volcano eruption from Nea Kameni similar to the one that occurred in 1950.
Santorini’s Crisis Period gave geologists important insight into the changes occurring below the ocean floor. As magma rises through the Earth’s crust and into the evolving chamber, the probability of an impending eruption continues to grow. Unfortunately, today’s technology isn’t capable of accurately predicting Santorini’s next eruption; geologists can only continue to monitor the caldera and wait for the sea floor to communicate with us once again.
(1). Vougioukalakis, Georges. 2014, “Santorini Volcano Hazard Assessment: The 2011-2012 volcanic unrest,” (PowerPoint Presentation).
(2) Newman, A., Stiros, S., Feng, L., Psimoulis, P., Moschas, F.,
Saltogianni, V., Jiang, Y., Papazachos, C., Panagiotopoulos, D.,
Karagianni, E., and Vamvakaris, D., 2012, Recent geodetic unrest at Santorini Caldera, Greece, Geophysical Research Letters, V39, L06309.