A 17-benchmark geodetic network was set up in 1982, located in the southern part of the caldera. The network was used to conduct triangulation, trilateration and levelling profiles. No displacements were found from 1982 to 2000 during the observation of both the geodetic network and levelling profile (M.J. Sevilla, 2002, personal communication with Fernández).
InSAR 1992 – 2000 (Fernández et al., 2003): 1) No deformation took place in the Las Cañadas caldera between 1993 and 2000, in agreement with other geodetic data; and 2) two localised areas of subsidence on the volcano flanks located in the region where the most recent eruptions occurred (Montaña Negra 1706, Chahorra 1798, Chinyero 1909): Garachico and Chı́o deformations. Garachico subsided by ~10cm over this period, extending over 15 km^2. Chı́o subsided by 3 cm, extending over 8 km².GPS 2000 (Fernández et al., 2003): A GPS network was set up, using the previous network locations, and observed from 5 to 12 August 2000. The GPS results largely confirm the InSAR results. InSAR data, coupled with GPS, between 1992 to 2005 reveal (Fernández et al., 2009): 1) three distinct small areas of high subsidence located outside the caldera at the NW and NE rifts; 2) a lower subsidence area in the south rift ; (iii) a large-scale deformation pattern following the outline of the island, extending well beyond caldera rim. The shape and position of this signal coincides with the extent of the dense core of the island (Fernández et al., 2009).
The signals associated with 1 and 2 are in areas characterized by less-dense or more-fracturated material relatively to the surroundings. Thus Fernández et al. (2009) interpret deformation is due to water table variations, interaction with existing fractures or to seismo-volcanic unrest. The large-scale deformation is interpreted to be related to gravitational sinking of the dense core of the island into a weak lithosphere.