50 years of steady ground deformation in the Altiplano-Puna region of southern Bolivia

Abstract

The Altiplano-Puna Volcanic Complex of the Central Andes is host to an ~150-km-wide, quasi-circular ground deformation anomaly centered on Uturuncu volcano (Bolivia). The precise onset and duration of this deformation is unclear, but geomorphologic studies bracket its initiation at less than a few hundred years ago. Here we report on the deformation history over an ~50 yr period by deriving orthometric height changes from leveling and global navigation satellite system (GNSS) observations at 53 benchmarks along a regional leveling line that crosses the deformation anomaly. The comparison of interferometric synthetic aperture radar (InSAR) line-of-sight (LOS) displacements and LOS-projected orthometric ground velocities in a common reference frame reveal central uplift extending to ~35 km from Uturuncu at a maximum orthometric rate of 1.2 cm yr-1 , and peripheral subsidence at a maximum rate of 0.3 cm yr-1 to ~60 km from Uturuncu. This pattern is consistent with the spatial extent and average rate of deformation observed by InSAR. Our interpretation of the data is that long-wavelength ground uplift at Uturuncu has likely occurred at a quasi-constant rate for at least half of a century. This study bridges the observational time spans between modern satellite geodetic observations (up to a few decades) and geomorphological observations (a few centuries and longer) of the recent deformation history of the continental crust in the Central Andes and adds to a select group of case studies of quantifiable long-term volcano deformation worldwide.

Synthesis: PLUTONS: Investigating the relationship between pluton growth and volcanism in the Central Andes

“…The sombrero is superimposed on an ~1-km-high topographic anomaly across the APVC with a wavelength of ~230 km (Perkins et al, 2016b). The deformation seems to have been ongoing from at least 1965-2010 with a maximum uplift rate of 1.2 ± 0.1 cm/yr and subsidence of 0.3 ± 0.03 cm/yr coincident with the interferometric synthetic aperture radar (InSAR) observed uplift and subsidence (Gottsmann et al, 2017). But, the rate is variable-in the 1990s, vertical rates are greater than 0.7 ± 2 cm/yr at GPS station UTUR; rates decrease to 0-0.1 cm/yr in 2010 and then increase to 0.9 cm/yr in 2015 .…”

“…Possible processes include an active diapir (e.g., Fialko and Pearse, 2012;del Potro et al, 2013) and the transfer of magma and magmatic fluids from deeper to shallower levels within a large-scale mushy magma system (Fialko and Pearse, 2012;Pritchard, 2013, 2017;Gottsmann et al, 2017;Sparks and Cashman, 2017). A mid-crustal source is consistent with the lack of gravity change associated with the deformation (Gottsmann et al, 2017). We discuss the merits and limits of these models in the section on "Conceptual Models for Deformation at Uturuncu and Lazufre.…”

“…How does the ground deformation at Uturuncu and Lazufre relate to the model of batholith formation and eruption potential discussed above? Previous work inferred that a magma intrusion was the most likely cause of deformation because of the deep sources at Lazufre (8-14 km below the surface; e.g., Pearse and Lundgren, 2013;Remy et al, 2014) and Uturuncu (6-19.5 km below the surface; e.g., Hickey et al, 2013, andGottsmann et al, 2017). The hydrothermal systems are considered to be shallower (e.g., Pritchard and Simons, 2002;Sparks et al, 2008).…”

“…This narrow range of parameters, while possible, may not be very likely. An alternative conceptual model is that supercritical fluids from the partially molten zones at depths >10 km at Lazufre and Uturuncu could become temporarily trapped, causing pressurization of a subsurface reservoir and ground uplift (e.g., Gottsmann et al, 2017). Such a model has been proposed for Soufriére Hills Volcano, Montserrat (Christopher et al, 2015;Sparks and Cashman, 2017), although these papers do not explore the implications of the model for ground deformation.…”

Multiscale Analysis of DInSAR Measurements for Multi-Source Investigation at Uturuncu Volcano (Bolivia)

“…The Andean Central Volcanic Zone represents one of the largest updoming volcanic regions on Earth [1,2], in which almost at its center the Uturuncu volcano (southwestern Bolivia) lies ( Figure 1). The magmatism of this area is the result of eastwards subduction of the Nazca oceanic plate beneath the South American continent [3,4].…”