Laccolith evolution during and after the 2011-12 eruption of Cordon Caulle volcano, Chile, from satellite feature-tracking, elevation, and thermal observations

Abstract:

The interplay between magmatic intrusions and volcanic eruption phases is poorly known due to the difficulties of field observations. The 2011-2012 effusive and explosive rhyolitic eruption of Cordon Caulle volcano, Chile with the coincident formation of a laccolith, provides a unique opportunity to study these processes because of the diverse remote sensing datasets available. We examine the ground deformation and surface temperature changes during and after the laccolith intrusion at Cordon Caulle using satellite synthetic aperture radar (SAR) feature tracking, satellite-derived elevation data, and thermal infrared (TIR) imagery. The syneruptive intrusion led to a ground uplift of over 200 m in less than 9 months immediately east of the active vent. Specifically, we analyze pairs of SAR images taken by the Envisat and TerraSAR-X satellites spanning June 2011 to March 2012 separated with a duration of 30 days or less. Our results show that the surface deformation associated with laccolith formation began within ~1 km of the active vent before June 7, 2011, including the western side where the lava flow erupts from starting on June 15. The maximum surface offset is ~160 m due to mostly uplift. The extent of the deformation roughly corresponds to areas with an elevated thermal anomaly revealed by TIR data from June-July 2011, supporting the relationship between the uplift and the intrusion. The surface continued to rise after the effusive phase started, but feature offsets indicative of subsidence replaced the uplift signal in mid-July and lasted until at least the end of 2011. This subsequent subsidence agrees with elevation differences using TanDEM-X DEMs, which show a maximum elevation loss of ~40 m between August 2011 and March 2012. TIR data from 2011-2012 also suggest that the thermal contraction of the laccolith cannot solely cause the subsidence, thus further magma migration out of the laccolith body is required. Our analysis provides a time series of laccolith inflation and deflation, which is essential for understanding the magma plumbing related to the eruption and post-emplacement dynamics of the laccolith. Given the fast evolution of the magmatic intrusion at Cordon Caulle, we highlight the need for satellite and other data with a higher temporal resolution than currently available.