Yes, Greece is home to several volcanoes, many of which are part of a major geological system located in the southern Aegean Sea. The most well-known volcanic centers are concentrated in a specific region, shaping the unique landscapes of the Greek islands. This geological setting has been responsible for some of the largest eruptions in Earth’s history.
The Tectonic Forces Shaping Greece
The presence of volcanoes in the Aegean region is a direct consequence of the collision between the African Plate and the Eurasian Plate. The African Plate is converging with and being forced beneath the smaller Aegean Sea Plate in a process known as subduction, which occurs along the Hellenic Subduction Zone south of Crete.
As the African Plate descends, intense heat and pressure cause water to be released from the slab. This water rises and lowers the melting point of the overlying mantle rock, generating magma deep beneath the surface, which then rises through the overriding crust.
This continuous subduction provides the magma source for the volcanoes. The African Plate is moving underneath the Aegean Sea Plate at an estimated rate of about 35 millimeters per year, making the Aegean Sea one of the most seismically active areas in the western Eurasian plate.
The Hellenic Volcanic Arc
The Hellenic Volcanic Arc, also known as the South Aegean Volcanic Arc, is the surface manifestation of the subduction zone’s magmatic activity. This arc is a curved chain of islands and submarine volcanoes extending approximately 500 kilometers. It stretches from the Saronic Gulf near the Greek mainland, through the Cyclades islands, and eastward toward the Turkish coast.
The arc includes several distinct volcanic centers, making it a geologically active corridor through the Aegean Sea. It is positioned north of the Hellenic Trench, which marks the boundary where the African Plate begins its descent.
The most prominent islands that form the arc include Methana, Milos, Santorini, and Nisyros. These islands feature a wide range of volcanic products, indicating a diverse and long-lived magmatic history spanning 3 to 4 million years.
Status and Major Volcanic Centers
The Hellenic Volcanic Arc contains at least five major volcanic centers that have been active in the last 12,000 years, classified as Holocene volcanoes. The three most frequently mentioned active centers are the Santorini volcanic complex, the Milos volcanic field, and the Nisyros volcano. All these sites are closely monitored by geological observatories.
Santorini
Santorini, officially Thera, is the most famous and most active volcanic center in the entire arc. Its most devastating event was the Minoan Eruption, an enormous caldera-forming eruption that occurred around 1610 BCE, making it one of the largest volcanic events in recorded history.
Today, the crescent-shaped island surrounds a seawater-filled caldera. Within this caldera lie the younger islands of Nea Kameni and Palea Kameni, formed by more recent eruptions, with the last small eruption occurring in 1950.
Nisyros
Further east, Nisyros is an active composite volcano, distinguished by a large caldera and ongoing hydrothermal activity. While the last magmatic eruption occurred thousands of years ago, Nisyros experienced multiple steam-driven (phreatic) explosions in the 19th century, most recently in 1888.
Geothermal drilling has indicated the presence of molten rock at shallow depths, between three and five kilometers beneath the surface.
Milos and Other Sites
Milos is characterized by an extensive volcanic field that exhibits significant geothermal activity, including hot springs and fumaroles. Although its last confirmed eruption was in 140 CE, the island’s geological features show it remains active beneath the surface.
Other notable active sites include the Methana peninsula and the submarine Kolumbo volcano northeast of Santorini, which erupted violently in 1650 CE.