We use ALOS-1 interferometric synthetic aperture radar data spanning the period of 2007-2011 to obtain time-dependent ground deformation data over Taal caldera related to the 2010-2011 volcanic unrest, which did not lead to an eruption. We employ finite element models that account for subsurface thermomechanical properties to test for viscoelastic deformation. We also examine the variability of crustal rheological parameters of the temperature-dependent Arrhenius formulation for viscosity, to investigate the effects on surface deformation. Deformation at Taal is observed to be time dependent and explained by a linear rate of pressure increase in a shallow magma reservoir at 5-km depth within a hot and viscoelastic upper crust. The best-fitting rheological properties of the local setting are consistent with either a felsic or hydrothermally altered uppermost crust. We show the significantly different effects that the variation of rheological parameters has on surface deformation, highlighting the importance of incorporation into future studies of deformation at different volcanic settings.Recent viscoelastic models of volcano deformation have used the Arrhenius formulation (see section 3.3.3) to estimate the viscosities of the medium (e.g., Gregg et al., 2012;Hickey et al., 2015), employing commonly used variables within the formulation that are potentially representative of the composition and temperatures of the subsurface, without full exploration of their potential values. Understanding the possible variations within these parameters along with their implications is critical to depict realistic rheological scenarios. It is also crucial for future studies that aim to understand crustal deformation, magma reservoir failure, intrusion propagation, and eruption forecasting.

Cotopaxi volcano started a period of volcanic unrest in April 2015 that led to a series of eruptions between August and November 2015. We use COSMO‐SkyMed Interferometric Synthetic Aperture Radar supported by continuous GPS observations spanning the period of 2014–2016 to obtain time‐dependent ground deformation data over Cotopaxi volcano related to the period of unrest and onset of eruptions. We find evidence of precursory deformation, with a maximum uplift on the western flank of 3.4 cm from April to August 2015. Deformation is explained by an inclined sheet intrusion located a few km southwest of the summit with an opening volume of 6.8 × 106 m3, extending from a depth of 12.1 km and shallowing to 5.5 km below the summit, that contributed to internal edifice growth. The temporal coincidence of deformation prior to the eruptions potentially suggests that short‐term eruptions at Cotopaxi are partly controlled by episodic edifice growth.

We use ALOS‐1 Interferometric Synthetic Aperture Radar data spanning the period of 2007–2011 to obtain time‐dependent ground deformation data over all of the volcanoes in Colombia, Ecuador, and Peru. We detect deformation on or near the proximity of Galeras, Reventador, Tungurahua, Guagua Pichincha, Sangay, and Cerro Auquihuato volcanoes, uncovering previously undocumented deformation in the latter three. Deformation is attributed to changes in pressurization of the volcanic systems (Galeras, Tungurahua, Guagua Pichincha, and Cerro Auquihuato), subsidence associated with flow deposits (Reventador), and flank creep (Sangay). Our models suggest that the pressure sources are located at depths of ∼1–6 km from the surface, indicating that the measurable deformation within our data is restricted to shallow magma chambers and hydrothermal systems.

Bulusan, Kanlaon, and Mayon volcanoes have erupted over the last decade, and Taal caldera showed signs of volcanic unrest within the same time range. Eruptions at these volcanoes are a threat to human life and infrastructure, having over 1,000,000 people living within 10 km from just these 4 volcanic centers. For this reason, volcano monitoring in the Philippines is of extreme importance.We use the ALOS-1 satellite from the Japanese Aerospace Exploration Agency (JAXA) to make an InSAR time series analysis over Bulusan, Kanlaon, Mayon, and Taal volcanoes for the 2007-2011 period. Time-dependent deformation was detected at all of the volcanoes.Deformation related to changes in pressurization of the volcanic systems was found on Taal caldera and Bulusan volcanoes, with best fitting Mogi sources located at half-space depths of 3.07 km and 0.5 km respectively.