Going to Santorini and staying near the cliffside of the caldera rim results in a special experience of the volcano. Each time I look out at the ocean, the new volcano in the center of the caldera is the central point to the most spectacular view I have ever seen. As a budding young geologist, I am in awe of how close I am to an active resurgent shield amidst a volcanic complex with such a rich history. I am excited to not only learn about the history but to track the emergence and construction of Santorini’s new volcanic field.
The island of Santorini has had a tumultuous history. As many as six eruptive stages have occurred to shape the island in southern Aegean Sea today. The most recent cataclysmic event was the Minoan eruption 3600 years ago forming three islands: Thira, Thirasia, and Aspronisi. The orientation of these islands appear circular and are the last remains of the volcanic complex destroyed in the Minoan eruption.
Since this ultra-plinian eruption, the volcano has been rebuilding, creating the Kameni Islands. Palea Kameni and Nea Kameni islands are two shield volcanoes centered in the Santorini caldera. Shield volcanoes are characterized by thin lava flows and have relatively low explosivity. Because these flows are thin, they stack on top of one another and can build some of the largest volcanoes in the world. The Kameni Islands have built up from the caldera floor 500 meters to reach 114 meters above sea level.
Their location is important in understanding the tectonic setting of Santorini. A fault running northeast-southwest cuts through the caldera and is referred to as the Kameni line(1). This fault allows better access for magma which tends to follow a path of least resistance. The Kameni Islands are on top of the fault and are aligned in the same direction due to the magma surfacing like grass in the cracks of a sidewalk.
Both Palea Kameni and Nea Kameni are unique in composition. Most shield volcanoes on Earth are basaltic, however Palea and Nea Kameni are dacitic (1). Magma compositions range from mafic to felsic depending on their weight percentage of silica. Mafic to felsic magmas produce basalt to rhyolite extrusive, or volcano forming, rocks. Dacite falls between these two types therefore it is considered intermediate in composition.
Intermediate magma indicates a transition period for the magma chamber feeding the Kameni Islands. Magma chambers typically begin as mafic, with lower silica content. Eruptions, interior crystallization of magma within the chamber, and the mixing of different magmas can all contribute to increase the percent of silica and create more felsic magma. Basaltic eruptions that predate the Kameni Islands are found to the south on Akrotiri peninsula. Assuming the same magma chambers feeds both locations, this supports the theory of an evolving magma chamber creating the Kameni Islands.
Palea Kameni, or “old cauldron” in English, began erupting in 46 AD. Dacitic domes, flows, and ejected tephra began as the initial submarine volcano rose above sea level and created the Thira lavas(1). Another eruption occurred to the north, the Agios Nikolaos lavas, in 726 AD. Almost a thousand years passed before the next eruptions when the magma vent shifted northeast along the Kameni Line to build Nea Kameni.
While researching the Kameni Island’s volcanic activity, I found a diagram outlining the different erupted lava units and their dates (2). I decided I wanted to create a map that would allow me to travel through two thousand years and see the evolution of the Kameni Islands. Below are the maps I illustrated and they allow you to see the islands’ progression with each new eruption and how Santorini caldera began its rebuilding process.
The Kameni Islands are the most recent eruptions in Santorini and are evidence for an active magma chamber under the caldera. Over time, the shield volcanoes will build and the magma chamber will evolve more to create other types of volcanoes and more dangerous eruptions. The Kameni Islands could be the beginning steps towards another catastrophic eruption.
Stay tuned: On June14th we will be traveling on a private boat tour to the Kameni Islands and have a guest geologist, Georges Vougioukalakis, from the Greek Institute of Geology and Mineral Exploration.
Druitt, T.H., Edwards, L., Mellors, R.M., Pyle, D.M., Sparks, R.S.J., Lanphere, M., Davies, M., and Barriero, B., 1999. Santorini Volcano. Geol Soc Mem, N19, 165p.
Fytikas, M., and Vougioukalakis, G.E., 2005. The South Aegean Active Volcanic Arc: Present Knowledge and Future Perspectives. Developments in Volcanology, N7, 381p.