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Hot stuff – 15 years of satellite data over Mt. 
Using radar images acquired by ESA satellites from 1992 to 2006, scientists have for the first time been able to monitor the long-term behaviour of Mt. Etna, Europe's highest and most active volcano. This unprecedented time series of Synthetic Aperture Radar (SAR) observations from ESA’s ERS-1, ERS-2 and Envisat satellites provided crucial information for understanding how the volcano’s surface deformed during the rise, storage and eruption of magma.
Changes in surface deformation, such as sinking, bulging and rising, are indicators of different stages of volcanic activity, which may result in eruptions. Thus, precise monitoring of a volcano’s surface deformation, or ‘breathing’, could lead to predictions of eruptions.
Based on the deformation measurements retrieved from their InSAR analysis during the 1992-2006 time interval and on the recorded volcanic data, the team distinguished two volcano-tectonic behaviours.
"Between 1993 and 2000, Etna inflated with a deformation rate of about 1 cm per year that progressively reduced with time, nearly vanishing between 1998 and 2000. Moreover, several eruptions took place with the lava being erupted (at a relatively low rate) exclusively from the top of the volcano," said Riccardo Lanari from the Istituto per il Rilevamento Elettromagnetico dell’ Ambiente (IREA-CNR) in Naples, Italy.
The results of the study show how surface deformation relates to eruptive behaviour over a time span much larger than that of a single eruption. Consequently, the continuity of satellite data is essential for studying and possibly predicting future volcanic eruptions.
ESA remains committed to providing continuity to its SAR missions. As part of its Global Monitoring for Environment and Security (GMES) programme, ESA will launch five Sentinel satellites. Sentinel-1, expected to be launched in 2011, will ensure the continuity of SAR data with ERS-2 and Envisat.
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