Imaging magma storage beneath the Santorini volcano

Recent activity at the Santorini volcano suggests magma is currently accumulating a few kilometres below surface. My study aims to constrain the volume and location of melt beneath this volcano, using a high-resolution imaging technology that has been developed for petroleum exploration.

A large volcanic eruption at Santorini in ~1630 BCE is the most likely cause of the demise of the Minoan civilisation. Santorini is currently in a dome-forming phase, with the upward movement of the Earth’s surface at its most rapid and significant since the last eruption in 1939–1941, suggesting a large eruptible volume of magma (melt, volatiles and solid crystals) has accumulated in a shallow chamber. Seismic data were acquired across the Santorini Caldera in November–December 2015 by scientists from the University of Oregon, Aristotle University of Thessaloniki, National and Kapodistrian University of Athens and Imperial College London. This involved firing airguns at sea to generate seismic waves, which were then recorded on seismometers placed on the ocean bottom and on the islands of Santorini, Anafi, Anydros and Christiana.


Experimental geometry figure.

The aim of this experiment is to use these seismic data to image the magma plumbing system beneath this volcano, and identify where melt is stored between the surface and base of the crust. We know that melt arriving from the mantle is rich in iron and magnesium (mafic), but that erupted magmas are more silicon-rich (felsic). We are less clear as to exactly where in the crust the magma evolves, and whether melt is stored in a series of isolated chambers or within a more continuous zone of partially-molten mush. 


Land seismometer site.

I will use a novel seismic technique, termed 3D full-waveform inversion, that is able to resolve subsurface physical properties at exceptionally high resolution. In recent years, this technology has been widely adopted by the petroleum industry, as it can improve images of oil reservoirs that lie beneath geologically complex rocks. In our experiment across Santorini, we have optimised the design of the experiment to allow us to take this technique and use it to resolve relatively fine-scale physical properties throughout the entire crust. With these properties, together with geochemical and petrological data from erupted lavas, we will be able to distinguish between competing models of subsurface melt storage, constrain the eruptible volume of melt that has recently accumulated in the shallow subsurface, and better understand magma systems beneath arc volcanoes, thus improving our ability to identify and predict volcanic hazards.
 
Professor Jo Morgan
Imperial College London
Research Project Grant