From the AGU Geophysical Research Letters: Recent geodetic unrest at Santorini Caldera
- Santorini is deforming appreciably for the 1st time since its last eruption
- A dense GPS network has unprecedented data coverage
- Activity is centered in the region that blew-out in the 1650 BC Minoan Eruption
In 1650 B.C.E., a series of massive volcanic eruptions decimated the ancient seafaring Minoan civilization. Over the next 4 millennia, the largely subaquatic Santorini caldera had a series of smaller eruptions, with five such events within the past 600 years, and ending most recently in 1950. From the air, the Santorini caldera appears as a small cluster within the larger collection of Greek islands in the southern Aegean Sea. Following a 60-year lull, Santorini woke up on 9 January 2011 with a swarm of low-magnitude earthquakes.
A GPS monitoring system installed in the area in 2006 gave Newman et al. a stable background against which to compare the effects of the reawakened volcano. By June 2011 the regional GPS stations showed that they had been pushed 5-32 millimeters (0.2-1.3 inches) farther from the caldera than they had been just six months earlier. Following these initial results, the authors bolstered the GPS network and conducted a more extensive survey in September 2011, which confirmed that the land near the volcano was swelling. Continued monitoring from September through January 2012 showed the expansion was accelerating, reaching a rate of 180 mm (7 in) per year.
Using a model that interpreted the source of the deformation as an expanding sphere, the authors suggest that the expansion is due to an influx of 14.1 million cubic meters (498 million cubic feet) of magma into a chamber 4-5 kilometers (2.5-3.1 miles) below the surface. The authors suggest that the ongoing expansion is not necessarily the signal of an impending eruption, adding that the recent swelling represents only a fraction of that which led to the Minoan eruption. However, they warn that even a small eruption could trigger ash dispersion, tsunamis, landslides, or other potentially dangerous activity.
Source: Geophysical Research Letters, doi:10.1029/2012GL051286, 2012 http://dx.doi.org/10.1029/2012GL051286.
Title: Recent Geodetic Unrest at Santorini Caldera, Greece
Authors: Andrew V. Newman: School of Earth and Atmospheric Sciences, Georgia Institute of Technology, USA;
Stathis Stiros, Fanis Moschas, and Vasso Saltogianni: Department of Civil Engineering, University of Patras, Greece;
Lujia Feng: Nanyang Technological University, Earth Observatory of Singapore, Singapore;
Panos Psimoulis: Institute of Geodesy and Photogrammetry, Switzerland;
Yan Jiang: University of Miami, Rosenstiel School of Marine and Atmospheric Sciences, USA;
Costas Papazachos, Dimitris Panagiotopoulos, Eleni Karagianni, and Domenikos Vamvakaris: Geophysical Laboratory, Aristotle University of Thessaloniki, Greece.
After approximately 60 years of seismic quiescence within Santorini caldera, in January 2011 the volcano reawakened with a significant seismic swarm and rapidly expanding radial deformation. The deformation is imaged by a dense network of 19 survey and 5 continuous GPS stations, showing that as of 21 January 2012, the volcano has extended laterally from a point inside the northern segment of the caldera by about 140 mm and is expanding at 180 mm/yr. A series of spherical source models show the source is not migrating significantly, but remains about 4 km depth and has expanded by 14 million m3 since inflation began. A distributed sill model is also tested, which shows a possible N-S elongation of the volumetric source. While observations of the current deformation sequence are unprecedented at Santorini, it is not certain that an eruption is imminent as other similar calderas have experienced comparable activity without eruption.