Archived data from the Envisat satellite show that the volcanic island of Santorini has recently displayed signs of unrest. Even after the end of its mission, Envisat information continues to be exploited for the long-term monitoring of volcanoes.
Santorini is a picturesque Greek island in the south Aegean Sea and the most active volcanic centre in the South Aegean Volcanic Arc. The island is the site of one of history's largest volcanic eruptions, about 3600 years ago. The geological record over the past million years reveals an extensive history of eruptions, with the most recent occurring in 1950.
But despite being dormant for over half a century, satellites have detected slight movements.
These and other findings were presented at the International Forum on Satellite Earth Observation for Geohazard Risk Management, currently under way in Santorini itself.
Organised by ESA in partnership with the Group on Earth Observations (GEO), the forum is focusing on the science and applications of satellite Earth observation to support the management of risks associated with geophysical hazards.
Seismic activity in Santorini, such as the underground movement of magma, from January 2011 to today has caused ground deformation that was detected by Envisat's radar.
Even from an orbit about 800 km above the ground, deformations of a few centimetres can be detected by satellite radars.
When two or more radar images of the same area are combined, changes in signal reflections between them can be measured. This technique called Differential Interferometric Synthetic Aperture Radar or DInSAR has become a useful tool for detecting ground deformation.
Envisat shows that the northeastern part of Santorini's Nea Kameni volcano experienced an uplift of about 5 cm in 2011, while other areas of the volcano rose some 3 cm.
"Monitoring to detect any change of the status of the volcano presents a
|Contact: Robert Meisner|
European Space Agency