Santorini volcano

SANTORINI VOLCANO – ΗΦΑΙΣΤΕΙΟ ΣΑΝΤΟΡΙΝΗΣ

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Giant ‘balloon of magma’ inflates under Santorini

Press release issued 9 September 2012

The chamber of molten rock beneath Santorini’s volcano expanded 10-20 million cubic metres – up to 15 times the size of London’s Olympic Stadium – between January 2011 and April 2012, according to a new survey carried out by an international team led by Oxford University and including a scientist from the University of Bristol. The research is reported in this week’s Nature Geoscience.

Aerial view of Nea Kameni island, Santorini showing the rugged shape of the island formed by lava flows during eruptions over the past 500 years; the photo is about 1 km across
Image by NERC Airborne Research and Survey Facility

People were obviously aware that something was happening to the volcano, but it wasn’t until we saw the changes in the GPS, and the uplift on the radar images that we really knew that molten rock was being injected at such a shallow level beneath the volcano. Many volcanologists study the rocks produced by old eruptions to understand what happened in the past, so it’s exciting to use cutting-edge satellite technology to link that to what’s going on in the volcanic plumbing system right now.

Dr Juliet Biggs

The growth of this ‘balloon’ of magma has seen the surface of the island rise 8-14 centimetres during this period, the researchers found. The results come from an expedition, funded by the UK’s Natural Environment Research Council, which used satellite radar images and Global Positioning System receivers (GPS) that can detect movements of the Earth’s surface of just a few millimetres.

The findings are helping scientists to understand more about the inner workings of the volcano which had its last major explosive eruption 3,600 years ago, burying the islands of Santorini under metres of pumice. However, it still does not provide an answer to the biggest question of all: ‘When will the volcano next erupt?’

In January 2011, a series of small earthquakes began beneath the islands of Santorini. Most were so small they could only be detected with sensitive seismometers but it was the first sign of activity beneath the volcano to be detected for 25 years.

Following the earthquakes Michelle Parks, an Oxford University DPhil student, spotted signs of movement of the Earth’s surface on Santorini in satellite radar images. Oxford University undergraduate students then helped researchers complete a new survey of the island.

Michelle Parks of Oxford University’s Department of Earth Sciences, an author of the paper, said: “During my field visits to Santorini in 2011, it became apparent that many of the locals were aware of a change in the behaviour of their volcano. The tour guides, who visit the volcano several times a day, would update me on changes in the amount of strong smelling gas being released from the summit, or changes in the colour of the water in some of the bays around the islands.

“On one particular day in April 2011, two guides told me they had felt an earthquake while they were on the volcano and that the motion of the ground had actually made them jump. Locals working in restaurants on the main island of Thera became aware of the increase in earthquake activity due to the vibration and clinking of glasses in their bars….”

Co-author, Dr Juliet Biggs of the University of Bristol’s School of Earth Sciences said: “People were obviously aware that something was happening to the volcano, but it wasn’t until we saw the changes in the GPS, and the uplift on the radar images that we really knew that molten rock was being injected at such a shallow level beneath the volcano. Many volcanologists study the rocks produced by old eruptions to understand what happened in the past, so it’s exciting to use cutting-edge satellite technology to link that to what’s going on in the volcanic plumbing system right now.”

Co-author Professor David Pyle of Oxford University’s Department of Earth Sciences, said: “For me, the challenge of this project is to understand how the information on how the volcano is behaving right now can be squared with what we thought we knew about the volcano, based on the studies of both recent and ancient eruptions. There are very few volcanoes where we have such detailed information about their past history.”

The team calculate that the amount of molten rock that has arrived beneath Santorini in the past year is the equivalent of about 10-20 years growth of the volcano. But this does not mean that an eruption is about to happen: in fact the rate of earthquake activity has dropped off in the past few months.

Paper

‘Evolution of Santorini Volcano dominated by episodic and rapid fluxes of melt from depth’ by Michelle M. Parks, Juliet Biggs, Philip England, Tamsin A. Mather, Paraskevi Nomikou, Kirill Palamartchouk, Xanthos Papanikolaou, Demitris Paradissis, Barry Parsons, David M. Pyle, Costas Raptakis and Vangelis Zacharis in Nature Geoscience

Cabot Institute

The Cabot Institute at the University of Bristol carries out fundamental and responsive research on risks and uncertainties in a changing environment. Our interests include natural hazards, food and energy security, resilience and governance, and human impacts on the environment. Our research fuses rigorous statistical and numerical modelling with a deep understanding of interconnected social, environmental and engineered systems – past, present and future. We seek to engage wider society – listening to, exploring with, and challenging our stakeholders to develop a shared response to twenty-first century challenges.

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NATURE GEOSCIENCE | ARTICLE (requires subscription)

Evolution of Santorini Volcano dominated by episodic and rapid fluxes of melt from depth

Nature Geoscience (2012) doi:10.1038/ngeo1562

Received 26 March 2012 - Accepted 03 August 2012 - Published online 09 September 2012

Authors

Affiliations

Department of Earth Sciences, University of Oxford, South Parks Road, Oxford, OX1 3AN, UK
- Michelle M. Parks,
- Philip England,
- Tamsin A. Mather,
- Kirill Palamartchouk,
- Barry Parsons &
- David M. Pyle
School of Earth Sciences, University of Bristol, Bristol, BS8 1RJ, UK
- Juliet Biggs
Department of Geology and Geoenvironment, University of Athens, Athens, Nomikou GR-15784, Greece
- Paraskevi Nomikou
School of Civil Engineering and Geosciences, University of Newcastle, Newcastle upon Tyne, NE1 7RU, UK
- Kirill Palamartchouk
Higher Geodesy Laboratory, National Technical University, Athens, NTUA GR-15780, Greece
- Xanthos Papanikolaou,
- Demitris Paradissis,
- Costas Raptakis &
- Vangelis Zacharis

Abstract

Santorini Volcano, the site of the catastrophic Minoan eruption in Greece, exhibits two distinct eruptive styles: small, effusive eruptions occur relatively frequently and build shields and domes of lava, whereas large explosive eruptions occur rarely, at intervals of 10,000–30,000 years. Both types of eruption were thought to incubate in a shallow magma chamber that is continually charged by small batches of melt injected into the chamber from below. However, petrological work suggests that at least 15% of the material ejected during the Minoan explosive eruption arrived in the magma chamber less than 100 years before the eruption. Here we use Satellite Radar Interferometry (InSAR) and Global Positioning System (GPS) measurements of surface deformation at Santorini to show that 10–20 million m³ of magma have been intruded beneath the volcano since January 2011. This volume is equivalent to 10–50% of the volumes of recorded dome-forming eruptions. GPS and triangulation data show that this is the only volumetrically significant intrusion to have occurred since 1955, shortly after the last eruption. Our observations imply that whether Santorini is in an explosive or dome-forming phase, its shallow magma chamber is charged episodically by high-flux batches of magma. The durations of these events are short in comparison with the intervening periods of repose and their timing is controlled by the dynamics of deeper magma reservoirs.

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University of Bristol (2012).
Giant ‘balloon of magma’ inflates under Santorini