Space‐geodetic evidence for multiple magma reservoirs and subvolcanic lateral intrusions at Fernandina Volcano, Galápagos Islands

Abstract

Using Interferometric Synthetic Aperture Radar (InSAR) measurements of the surface deformation at Fernandina Volcano, Galápagos (Ecuador), acquired between January 2003 and September 2010, we study the structure and the dynamics of the shallow magmatic system of the volcano. Through the analysis of spatial and temporal variations of the measured line‐of‐sight displacement we identify multiple sources of deformation beneath the summit and the southern flank. At least two sources are considered to represent permanent zones of magma storage given their persistent or recurrent activity. Elastic deformation models indicate the presence of a flat‐topped magma reservoir at ∼1.1 km below sea level and an oblate‐spheroid cavity at ∼4.9 km b.s.l. The two reservoirs are hydraulically connected. This inferred structure of the shallow storage system is in agreement with previous geodetic studies and previous petrological analysis of both subaerial and submarine lavas. The almost eight‐year‐long observation interval provides for the first time geodetic evidence for two subvolcanic lateral intrusions from the central storage system (in December 2006 and August 2007). Subvolcanic lateral intrusions could provide the explanation for enigmatic volcanic events at Fernandina such as the rapid uplift at Punta Espinoza in 1927 and the 1968 caldera collapse without significant eruption.

Observing eruptions of gas-rich compressible magmas from space

“…It is apparent that there is no clear relationship between erupted volume (dense rock equivalent, DRE) and the mass of sulfur gases emitted during an eruption6, creating challenges for reconstructing the magnitudes and climate impacts78 of past eruptions recorded as sulfate spikes in ice cores9 and for predicting the impacts of potential future eruptions. Geochemical and geophysical observations of volcanic eruptions are becoming ever more precise, frequent and spatially resolved101112, yet they are rarely considered in tandem, despite the fundamental link between them.…”

A two‐magma chamber model as a source of deformation at Grímsvötn Volcano, Iceland

“…However, many recent deformation studies that have been based on in situ measurements at Soufriere Hills Volcano [Elsworth et al, 2008;Foroozan et al, 2010Foroozan et al, , 2011Hautmann et al, 2013;Melnik and Costa, 2014] or InSAR data at Fernandina Volcano [Chadwick et al, 2011], Galapagos Islands [Bagnardi and Amelung, 2012], have revealed that the displacement field can only be satisfactorily interpreted by considering two magma reservoirs that are located on the same magma vertical path but at two different depths. On the other hand, all of the studies that have interpreted deformation data with two magma reservoirs and with connecting conduits or dikes have inverted the displacement fields to infer each source of deformation without taking into account the existing flow dynamics between these sources.…”

A Physical Model of Sill Expansion to Explain the Dynamics of Unrest at Calderas with Application to Campi Flegrei

“…Moreover, in many cases, the structure of the shallow plumbing system and the dynamic processes in calderas are consistent with the emplacement of sill-like magma intrusions (Okada, 1985;Amoruso et al, 2007;Onizawa et al, 2007;Jónsson, 2009;Chang et al, 2010;Woo and Kilburn, 2010;Chadwick et al, 2011;Maccaferri et al, 2011;Menand, 2011;Unglert et al, 2011;Bagnardi and Amelung, 2012;Manconi and Casu, 2012;Bagnardi et al, 2013;Corbi et al, 2015;D'Auria et al, 2015a;Richardson et al, 2015;Rivalta et al, 2015;Trasatti et al, 2015;Le Mével et al, 2016). Usually the intrusion of a sill is modeled as a pressure increase in a horizontal crack (e.g., Fialko et al, 2001;Woo and Kilburn, 2010) which causes deformations and ground uplift.…”