What’s Shaking Santorini?

Since January of 2025, the Greek island of Santorini has been bombarded by earthquakes.¹ Authorities declared a state of emergency on the island, closing schools and businesses, and evacuating thousands from their homes.¹ Obviously, the Greek authorities do not want to risk a potential natural disaster, especially considering the unusual nature of these earthquakes.

The recent earthquakes don’t follow typical earthquake trends. A typical earthquake has one big quake (called the “mainshock”) which is followed by smaller “aftershocks”.² Instead, these earthquakes began with many smaller quakes, then escalated to moderately sized, and then continued to have many moderate quakes.³ Sequences of earthquakes which display this trend, either staying at the same magnitude (the “power” of an earthquake) or even increasing in magnitude, are called earthquake swarms.

Due to the relative abnormality of earthquake swarms, many geologists were alarmed by the events, especially given the complex geologic history of the area. Santorini is a volcanic island—­its arc shape is what’s left of the volcano. The center of the volcano collapsed forming a caldera (the collapsed empty magma chamber left after an eruption). This was the result of an eruption around 3,600 years ago, which made the bay now in the middle of the island!⁴ The volcano that created Santorini, as well as others in the area, are still active—meaning they have the potential to erupt in the future. The last eruption of this volcano was in 1950, which is very recent in geological terms.⁵ʼ⁶

So, when the University of Athens recorded upwards of 12,800 earthquakes between January and the beginning of February, scientists began to worry.³ Initially the scientists worried that the earthquake swarm was being caused by magma moving beneath the caldera, which can be an indicator of a volcanic eruption. If an eruption did occur, it would be devastating for the island. Besides the quakes potentially indicating a volcanic eruption, they could also trigger powerful tsunamis.¹ Tsunamis can be caused by large earthquakes, underwater volcanic eruptions, and large amounts of water displaced by lava or landslides—all of which could happen with these earthquakes.⁴

So! All that potential catastrophe aside—what is actually causing the Santorini earthquake swarm? Geologists and seismologists analyzed data and modelling to make their best educated guesses as to what is happening. However, they haven’t come to a concrete answer, and likely never will. The entire field of geology in a nutshell is just finding the “most likely” scenario. The “most likely” scenario changes frequently, especially as new data comes out. So, what does this mean for the initial volcano hypothesis? Scientists currently believe the swarm is actually due to a combination of other (non-volcano-related) factors. The experts believe that because the earthquakes changed their origin to farther away from the volcano in Santorini, they likely indicate something else.

The latest theory is that the swarm is more likely caused by moving tectonic plates (the giant puzzle pieces of rock that make up the surface of Earth) and moving magma.⁷ Their theory goes like this: part of the African tectonic plate (the plate that has Africa on it) is underneath the Aegean tectonic plate (the plate with Santorini on it), and the part of the African plate that is already under the Aegean plate is sinking farther down into the Earth. The sinking part of the African plate is causing stress on the surface of the Aegean plate. This manifests in cracks (faults) in the Aegean plate on the ocean floor.⁸ The United States Geological Survey determined that these earthquakes are originating from faults that resulted from this kind of plate stress (tension)—which fits with this theory.⁹ Earthquake swarms, however, usually result from another process: fluids moving through a rock.² The scientists accounted for this and added to their theory that there are likely fluids (like magma or water) moving around underneath these faults, disturbing them and creating the swarm.¹⁰ The large majority of the earthquakes have been originating at the faults with fluids, so it makes sense that the combination of these theories is currently the most likely explanation for this onslaught of earthquakes.