Santorini Volcano lies 110 km north of Crete. It consists of five islands in a small, circular archipelago around a caldera measuring 12 by 7 km, with 200-300 m high, steep cliffs on three sides. It is one of the largest volcanic centres of the 500 km long South Aegean Volcanic Arc, which is due to subduction of the eastern Mediterranean crust beneath the Aegean region.

Santorini lies on a submarine rift zone extending from the extinct Christiana Volcano in the SW to the submarine Kolumbo chain of volcanoes in the NE, and is the largest centre of the group. The earliest recorded volcanism on Santorini took place about 700,000 years ago, and since 350,000 years ago the activity has been highly explosive, with over a hundred explosive eruptions of which a dozen or more were of plinian intensity and shed pyroclastic flows into the sea. Repeat times for major explosive eruptions on the islands are on the order of about 20,000 years, although this has been very variable.

The last large explosive eruption occurred in the late Bronze Age, probably around 1620 BCE, and laid down deposits of pumice and ash up to 50 m thick all over the islands. The eruption products buried an affluent contemporary town at the ancient site of Akrotiri, and may have impacted the Minoan civilization on Crete through a combination of tsunamis, ash fallout, acid rain and atmospheric ozone depletion. The eruption is considered to have been one of the largest in the past 10,000 years worldwide, and is an iconic event in both volcanology and archaeology. It impacted both local and regional cultures, and may have fueled the Atlantis legend.

The eruption formed the present-day caldera, which consists of three flat-floored basins: a large northern basin 390 m deep, and two smaller ones (western, 320 m and southern, 270m deep). In recent years the caldera has been the subject of state of the art marine research, including high-resolution bathymetric mapping and seismic studies of the caldera volcano-sedimentary fill. The Christiana-Santorini-Kolumbo volcanic line was also the subject of a major seismic tomography experiment in 2017.

Following the eruption in the late Bronze Age, a new caldera cycle has formed the islands of Nea and Palea Kameni in the centre of the caldera. These islands are in fact the summits of a single, mostly submarine edifice 400 m high that has produced over nine eruptions of lava in historical times. The earliest recorded eruption of Kameni Volcano was 197 BCE, and the last took place in 1950. Over 15 months in 2011-2012 the Kameni Islands were uplifted by several centimetres, and the level of microseismicity greatly increased, probably due to intrusion of new magma at a depth of about 4 km beneath the northern caldera basin.

Santorini had a 2011 census population of 15,550, but it attracts over 2 million tourists a year from all over the globe. The municipality includes the inhabited islands of Santorini and Therassia and the uninhabited islands of Nea Kameni, Palea Kameni, Aspronisi, and Christiana. All urban settlements are considered as Historical and Cultural Heritage sites, and their development is protected and regulated by specific laws in terms of building materials and architecture. The traditional architecture of Santorini is similar to that of the other Cyclades islands, with low-lying cubical houses made of local stone and whitewashed or limewashed with various volcanic ashes used as colours. The two main sources of wealth on Santorini are agriculture and tourism, but it remains the home to a small, but flourishing wine industry.

The field trip will visit many key outcrops of volcanic products from the Bronze-Age and earlier eruptions. A boat tour of the caldera will enable us to climb Nea Kameni Island and examine the products of the many historical eruptions. A guided visit of the archaeological site of ancient Akrotiri will also be included.