This TerraSAR-X Differential SAR Interferogram of Eyjafjallajoekull Volcano, Iceland, represents the inflation of the subglacial volcano of more than 40 cm prior to the eruption on April 14, 2010. The observed surface deformation is caused by magma rising from a chamber into the summit reservoir. As a result of the inflation of the magma reservoir, the ground surrounding it increases in volume and the surface is uplifted.
The interferogram was created from two pre-eruption TerraSAR-X scenes: the first one recorded almost 10 months prior to the eruption and the second one just three days before the eruption. An ASTER DEM (Digital Elevation Model) was used to remove the topogaphic influence in the interferogram, which is superimposed onto an inverted amplitude image for visualisation purposes.
Each color cycle (fringe) represents a line-of-sight motion between the two acquisitions of 1.56 cm (= half X-band wavelength). The fringes vanish on the glacial area on top of the volcano due to temporal decorrelation of the radar signal. The decorrelation is caused by precipitation, glacier flow and other surface changes. About 20 fringes can be counted from the image margin to the glacier area which represent a total vertical uplift of approximately 40 cm. The actual vertical uplift is probably even higher than this number, as potential fringes in the glacial area were not taken into account.