Santorini caldera

Santorini is a group of islands in the sea.

Much of it is under the water. It has high, steep walls of rock.

Some small islands sit in the middle. These small islands are made of lava rocks. The big volcano is still active today. It can cause the ground to shake.

Scientists like to visit this special place. It is a very famous spot in Greece.

Santorini is a famous group of islands in Greece.

Most of it sits under the sea. This underwater bowl is called a caldera.

High, steep cliffs rise from the water. Some small islands sit in the center. These are the Kameni islands. They are made of lava rocks.

This area is part of a volcanic arc. A volcanic arc is a line of volcanoes.

This arc forms because one tectonic plate slides under another. This movement can cause earthquakes.

The volcano is still active today. It has many different stages of history. A big eruption happened about 3,600 years ago. This was the Minoan eruption. It caused the current caldera to form. Scientists also found a much larger eruption from long ago. That huge event happened 520,000 years ago.

In 2024, the volcano showed signs of unrest. The ground began to move and shake. This led to many earthquakes. Scientists watched the ground as it moved up. This activity shows that the volcano is still alive.

The Santorini caldera is a huge, mostly underwater bowl in the Aegean Sea.

It sits about 120 kilometers north of Crete in Greece. You can see a circular group of islands rising above the water. This group includes the main island of Santorini, also called Thera. Other islands like Therasia and Aspronisi sit around the edge. In the very center, there are two small islands called Nea Kameni and Palea Kameni.

The caldera has very high, steep cliffs on three sides. It is a very important place for scientists to study volcanoes.

This area works because of moving pieces of the Earth called tectonic plates. The African plate slides underneath the Aegean subplate. This movement happens at a rate of up to 5 centimeters every year. This sliding action can cause earthquakes deep underground.

Santorini is part of the South Aegean Volcanic Arc. This is a line of active volcanoes. The Santorini volcano is the most active part of this entire arc. The center islands, the Kameni islands, are made of dark lava rocks. These rocks were built up by smaller eruptions over time.

Scientists have studied the history of this volcano for a long time. The caldera has changed many times through different stages. A southern caldera formed about 180,000 years ago. Later, the Skaros caldera formed about 70,000 years ago. The Cape Riva caldera appeared about 21,000 years ago. The caldera we see today was created about 3,600 years ago. This happened during a massive event called the Minoan eruption. Some people think this huge eruption inspired the legend of Atlantis.

There have been many big eruptions in the past. One very large eruption happened about 520,000 years ago. This event was much bigger than the Minoan eruption. It produced flows of hot ash and rock that were huge.

The Minoan eruption was rated a 7 on the Volcanic Explosivity Index. This index helps scientists measure how powerful an eruption is. More recently, the volcano had its last eruption in 1950. Even though it is quiet now, it is still an active volcano. Scientists use GPS tools to watch how the ground moves.

In 2024, the volcano showed signs of unrest again. The ground began to shake with many earthquakes.

Scientists saw the ground inside the caldera slowly move upward. This is called inflation, which means the ground swells up. In early 2025, the shaking became very intense. This led to the evacuation of 11,000 people from the island. Scientists believe this happens when magma moves through cracks in the Earth. Watching these small changes helps experts prepare for the future.

The Santorini caldera is a massive, mostly submerged volcanic structure located in the southern Aegean Sea. It sits approximately 120 kilometers north of Crete in Greece.

Above the water, the caldera appears as a circular group of islands. This group includes the main island of Santorini, also known as Thera in antiquity. Other islands like Therasia and Aspronisi sit on the periphery. At the very center, the Nea Kameni and Palea Kameni islands rise from the water.

This site is so significant that it has been designated a Decade Volcano. It is also recognized as an IUGS Geological Heritage Site due to its international scientific relevance.

The formation of this caldera is driven by plate tectonics. The African tectonic plate is subducting, or sliding, underneath the Aegean subplate of the Eurasian tectonic plate. This subduction occurs at a rate of up to 5 cm per year in a northeasterly direction. This process creates intense pressure and causes earthquakes at depths of 150 to 170 km.

Santorini is the most active part of the South Aegean Volcanic Arc. This arc includes other active volcanoes like Methana, Milos, and Nisyros. The movement of these plates provides the energy that fuels the volcanic activity in the region.

The current volcanic complex has evolved through several distinct geological stages. It sits in the center of the Christiana-Santorini-Kolumbo volcanic field. This field includes the extinct Christiana Volcano and the submarine Kolumbo Volcano. The present-day caldera is made of overlapping shield volcanoes. These were shaped by at least four overlapping calderas over many thousands of years. The oldest southern caldera formed about 180,000 years ago. This was followed by the Skaros caldera 70,000 years ago and the Cape Riva caldera 21,000 years ago. The caldera we see today formed about 3,600 years ago during the Minoan eruption.

History shows that Santorini has experienced many catastrophic eruptive events. The Minoan eruption, occurring around 1610 BC, was a massive event. It involved central vent eruptions, submarine eruptions, and explosive pyroclastic flows. These flows are fast-moving currents of hot gas and volcanic matter. The Minoan eruption was so large it received a 7 on the Volcanic Explosivity Index (VEI). Some researchers suggest this event may have inspired the legend of Atlantis. However, an even larger eruption occurred roughly 520,000 years ago. This ancient eruption produced pyroclastic flows ten times larger than the 2022 Hunga Tonga–Hunga Haʻapai eruption. It also left volcanic deposits that were six times larger in volume than those of the Minoan eruption.

Even though the volcano is currently dormant, it remains an active system. The center islands, Nea and Palea Kameni, were built by smaller, submarine eruptions. These eruptions created dark-colored lava shields. The last recorded eruption of this type occurred in 1950. Since then, the volcano has mostly shown fumarolic activity, which is the release of volcanic gases. Scientists monitor the area closely using GPS and satellite measurements. In 2011 and 2012, instruments registered renewed deformation, meaning the shape of the ground began to change.

In recent years, Santorini has entered periods of significant volcanic unrest. Starting in mid-summer 2024, seismic activity increased significantly. Scientists observed slow deformation, or swelling, inside the caldera. Between January and February 2025, the ground showed rapid inflation. This means the surface moved vertically and westward by up to 7 mm per day. This intense shaking led to the evacuation of 11,000 people. Researchers identified four stages of this unrest. It moved from a fluid-influenced phase to a more regular tectonic sequence. This transition helps scientists understand when magma movement is shifting toward fault-controlled activity.

Understanding these patterns is vital for modern volcanology. In June 2025, a new seismic swarm was detected under the island. These earthquakes were mostly smaller than magnitude 3. They clustered at depths of 5 to 20 km along the Kameni line. This line is the main path for magma ascent. The swarm was triggered by magma moving through a fault system. While the earthquakes ended after three months, the magma remained underground. By studying the stability of the b-value, which measures how earthquake magnitudes are distributed, experts can better communicate hazards to the public.