EGU2020-7188, updated on 12 Jun 2020
https://doi.org/10.5194/egusphere-egu2020-7188
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Unrest episodes at Alcedo and Cerro Azul (Galapagos) revealed by InSAR data and geodetic modelling

Federico Galetto1, Andrew Hooper2, and Marco Bagnardi2,3
Federico Galetto et al.
  • 1Università degli Studi di Roma Tre, Department of Science, Rome, Italy (federico.galetto@uniroma3.it)
  • 2COMET, School of Earth and Environment, University of Leeds, Leeds, UK
  • 3NASA Goddard Space Flight Center, Greenbelt, MD, USA

Western Galápagos calderas experienced repeated eruptive and non-eruptive unrest in the last decades, only partially studied. Here we investigated, using the Synthetic Aperture Radar Interferometry (InSAR) and geodetic modelling, the eruptive and the non-eruptive unrest episodes occurred in two of the less studied calderas of the western Galápagos: Alcedo and Cerro Azul. Alcedo underwent repeated non-eruptive unrest from 2007 to 2011, while Cerro Azul experienced an unrest, from 2007 to 2008, culminated in two eruptive phases from May 29th to June 11th 2008. Results highlight how Alcedo experienced two episodes of uplift due to new magma injections in its shallow magma reservoir, separated by an episode with a limited lateral propagation of magma, probably interrupted for the lack of new magma supply in the magma reservoir. Results also hint to a possible relationship between these short-term unrest episodes and the longer-term process of resurgence at Alcedo. As for Cerro Azul, we overcame unwrapping errors affecting some of the InSAR data of Cerro Azul by proposing a new method, based on the wrapped phase differences among nearby pixels, to invert the wrapped phase directly. Our results highlight how the eruption was preceded by long-term pre-eruptive inflation (October 2007 – April 2008). During the first eruptive phase, most of the magma responsible for the inflation fed the lateral propagation of a radial dike, which caused a first deflation of the magmatic reservoir. During the second eruptive phase, the further lateral propagation of the dike fed a radial eruptive fissure at the base of the edifice, causing further deflation of the magmatic reservoir. From the first to the second eruptive phase, the radial dike changed its strike propagating towards a topographic low between Cerro Azul and Sierra Negra. An increase in magma supply from the reservoir to the dike promoted the further lateral propagation of the dike, confirming the importance of a continuous supply of magma in the propagation of a dike. 

How to cite: Galetto, F., Hooper, A., and Bagnardi, M.: Unrest episodes at Alcedo and Cerro Azul (Galapagos) revealed by InSAR data and geodetic modelling, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7188, https://doi.org/10.5194/egusphere-egu2020-7188, 2020

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Presentation version 1 – uploaded on 28 Apr 2020
  • CC1: Questions and answers from the live chat during EGU2020, Michael Heap, 11 May 2020

    Q: Can you briefly describe the advantages of your new software written in MATLAB?

    A: It allows to overcome unwrapping errors

    Q: Any clue why lateral propagation versus eruption is favored? Only a matter of the amount of magma available?

    A: The unrest at Alcedo was non-eruptive. The lateral propagation was aborted soon for the lack of new magma suppliy

    Q: Alcedo is reported to have rhyolites, whereas Cerro Azul has not. Any link perhaps with the surface deformation?

    A: I don't think. The rhyolites eruption was an isolated case in the eruètive hisrory of Alcedo.