Inflation-Deflation Episodes in the Hengill and Hrómundartindur Volcanic Complexes, SW Iceland

Cécile Ducrocq; Halldór Geirsson; Þóra Árnadóttir; Daniel Juncu; Vincent Drouin; Gunnar Gunnarsson; Bjarni R. Kristjánsson; Freysteinn Sigmundsson; Sigrún Hreinsdóttir; Sigrún Tómasdóttir; Hanna Blanck

doi:10.3389/feart.2021.725109

Inflation-Deflation Episodes in the Hengill and Hrómundartindur Volcanic Complexes, SW Iceland

Cécile Ducrocq^*, Halldór Geirsson, Þóra Árnadóttir, Daniel Juncu, Vincent Drouin, Gunnar Gunnarsson, Bjarni R. Kristjánsson, Freysteinn Sigmundsson, Sigrún Hreinsdóttir, Sigrún Tómasdóttir, Hanna Blanck

^*Corresponding author for this work

Research output: Contribution to journal › Article › peer-review

Abstract

Non-eruptive uplift and subsidence episodes remain a challenge for monitoring and hazard assessments in active volcanic systems worldwide. Sources of such deformation may relate to processes such as magma inflow and outflow, motion and phase changes of hydrothermal fluids or magma volatiles, heat transfer from magmatic bodies and heat-mining from geothermal extraction. The Hengill area, in southwest Iceland, hosts two active volcanic systems, Hengill and Hrómundartindur, and two high-temperature geothermal power plants, Hellisheiði and Nesjavellir. Using a combination of geodetic data sets (GNSS and InSAR; Global Navigation Satellite Systems and Interferometry Synthetic Aperture Radar, respectively) and a non-linear inversion scheme to estimate the optimal analytical model parameters, we investigate the ground deformation between 2017–2018. Due to other ongoing deformation processes in the area, such as plate motion, subsidence in the two geothermal production fields, and deep-seated source of contraction since 2006, we estimate 2017–2018 difference velocities by subtracting background deformation, determined from data spanning 2015–2017 (InSAR) or 2009–2017 (GNSS). This method highlights changes in ground deformation observed in 2017–2018 compared to prior years: uplift signal of ∼10 km diameter located in the eastern part of the Hengill area, and geothermal production-related temporal changes in deformation near Húsmúli, in the western part of the Hengill area. We find an inflation source located between the Hengill and Hrómundartindur volcanic complexes, lasting for ∼5 months, with a maximum uplift of ∼12 mm. Our model inversions give a source at depth of ∼6–7 km, located approximately in the same crustal volume as an inferred contracting source in 2006–2017, within the local brittle-ductile transition zone. No significant changes were observed in local seismicity, borehole temperatures and pressures during the uplift episode. These transient inflation and deflation sources are located ∼3 km NW from a source of non-eruptive uplift in the area (1993–1999). We consider possible magmatic and hydrothermal processes as the causes for these inflation-deflation episodes and conclude that further geophysical and geological studies are needed to better understand such episodes.

Original language	English
Article number	725109
Journal	Frontiers in Earth Science
Volume	9
DOIs	https://doi.org/10.3389/feart.2021.725109
Publication status	Published - 11 Oct 2021

Bibliographical note

Funding Information:
We are very thankful to Thorsteinn J?nsson, Sveinbj?rn Steinth?rsson and students for assistance in the GNSS data collection over the years. We acknowledge UNAVCO and National Land Survey of Iceland for sharing their GNSS equipments. We are grateful to the National Land Survey of Iceland and Iceland GeoSurvey for sharing of their GNSS campaign data sets. We extend the gratitude to Benedikt G. ?feigsson and Icelandic Meteorological Office for the maintenance of continuous GNSS stations. We are thankful to the Copernicus and European Space Agency for the free access data sets of Sentinel-1. We fully acknowledge the satellite data sets provided by the German Aerospace Center used in the study: the TanDEM-X DEM (project IDEM_GEOL0123) and TerraSAR-X images provided through the Icelandic Volcanoes Supersite project (http://geo-gsnl.org/supersites/permanent-supersites/iceland-volcanoes-supersite/) through the Committee on Earth and Observing Satellites (CEOS). Most of the figures were created using the GMT software v.6.0.0 (Wessel et al., 2019). The high resolution digital elevation model used in Figure 1 is derived from the Arctic DEM (Porter et al., 2018) modified by the National LandSurvey of Iceland (2020). Comments on the drafts from Gu?finna Th. A?algeirsd?ttir (University of Iceland) were particularly appreciated. We thank two reviewers for their comments and suggestions which improved the manuscript.

Funding Information:
This work was funded via the Icelandic Research Fund, grant 174377-015 and NordVulk fellowship programme 2020.

Publisher Copyright:
© Copyright © 2021 Ducrocq, Geirsson, Árnadóttir, Juncu, Drouin, Gunnarsson, Kristjánsson, Sigmundsson, Hreinsdóttir, Tómasdóttir and Blanck.

Other keywords

joint inversion
satellite geodesy
time-series analysis
volcano deformation
volcano monitoring

Access to Document

10.3389/feart.2021.725109

Cite this

@article{6a221071e6ee47409b4365b7f185d68c,

title = "Inflation-Deflation Episodes in the Hengill and Hr{\'o}mundartindur Volcanic Complexes, SW Iceland",

abstract = "Non-eruptive uplift and subsidence episodes remain a challenge for monitoring and hazard assessments in active volcanic systems worldwide. Sources of such deformation may relate to processes such as magma inflow and outflow, motion and phase changes of hydrothermal fluids or magma volatiles, heat transfer from magmatic bodies and heat-mining from geothermal extraction. The Hengill area, in southwest Iceland, hosts two active volcanic systems, Hengill and Hr{\'o}mundartindur, and two high-temperature geothermal power plants, Hellishei{\dh}i and Nesjavellir. Using a combination of geodetic data sets (GNSS and InSAR; Global Navigation Satellite Systems and Interferometry Synthetic Aperture Radar, respectively) and a non-linear inversion scheme to estimate the optimal analytical model parameters, we investigate the ground deformation between 2017–2018. Due to other ongoing deformation processes in the area, such as plate motion, subsidence in the two geothermal production fields, and deep-seated source of contraction since 2006, we estimate 2017–2018 difference velocities by subtracting background deformation, determined from data spanning 2015–2017 (InSAR) or 2009–2017 (GNSS). This method highlights changes in ground deformation observed in 2017–2018 compared to prior years: uplift signal of ∼10 km diameter located in the eastern part of the Hengill area, and geothermal production-related temporal changes in deformation near H{\'u}sm{\'u}li, in the western part of the Hengill area. We find an inflation source located between the Hengill and Hr{\'o}mundartindur volcanic complexes, lasting for ∼5 months, with a maximum uplift of ∼12 mm. Our model inversions give a source at depth of ∼6–7 km, located approximately in the same crustal volume as an inferred contracting source in 2006–2017, within the local brittle-ductile transition zone. No significant changes were observed in local seismicity, borehole temperatures and pressures during the uplift episode. These transient inflation and deflation sources are located ∼3 km NW from a source of non-eruptive uplift in the area (1993–1999). We consider possible magmatic and hydrothermal processes as the causes for these inflation-deflation episodes and conclude that further geophysical and geological studies are needed to better understand such episodes.",

keywords = "joint inversion, satellite geodesy, time-series analysis, volcano deformation, volcano monitoring",

author = "C{\'e}cile Ducrocq and Halld{\'o}r Geirsson and {\TH}{\'o}ra {\'A}rnad{\'o}ttir and Daniel Juncu and Vincent Drouin and Gunnar Gunnarsson and Kristj{\'a}nsson, {Bjarni R.} and Freysteinn Sigmundsson and Sigr{\'u}n Hreinsd{\'o}ttir and Sigr{\'u}n T{\'o}masd{\'o}ttir and Hanna Blanck",

note = "Funding Information: We are very thankful to Thorsteinn J?nsson, Sveinbj?rn Steinth?rsson and students for assistance in the GNSS data collection over the years. We acknowledge UNAVCO and National Land Survey of Iceland for sharing their GNSS equipments. We are grateful to the National Land Survey of Iceland and Iceland GeoSurvey for sharing of their GNSS campaign data sets. We extend the gratitude to Benedikt G. ?feigsson and Icelandic Meteorological Office for the maintenance of continuous GNSS stations. We are thankful to the Copernicus and European Space Agency for the free access data sets of Sentinel-1. We fully acknowledge the satellite data sets provided by the German Aerospace Center used in the study: the TanDEM-X DEM (project IDEM_GEOL0123) and TerraSAR-X images provided through the Icelandic Volcanoes Supersite project (http://geo-gsnl.org/supersites/permanent-supersites/iceland-volcanoes-supersite/) through the Committee on Earth and Observing Satellites (CEOS). Most of the figures were created using the GMT software v.6.0.0 (Wessel et al., 2019). The high resolution digital elevation model used in Figure 1 is derived from the Arctic DEM (Porter et al., 2018) modified by the National LandSurvey of Iceland (2020). Comments on the drafts from Gu?finna Th. A?algeirsd?ttir (University of Iceland) were particularly appreciated. We thank two reviewers for their comments and suggestions which improved the manuscript. Funding Information: This work was funded via the Icelandic Research Fund, grant 174377-015 and NordVulk fellowship programme 2020. Publisher Copyright: {\textcopyright} Copyright {\textcopyright} 2021 Ducrocq, Geirsson, {\'A}rnad{\'o}ttir, Juncu, Drouin, Gunnarsson, Kristj{\'a}nsson, Sigmundsson, Hreinsd{\'o}ttir, T{\'o}masd{\'o}ttir and Blanck.",

year = "2021",

month = oct,

day = "11",

doi = "10.3389/feart.2021.725109",

language = "English",

volume = "9",

journal = "Frontiers in Earth Science",

issn = "2296-6463",

publisher = "Frontiers Media SA",

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TY - JOUR

T1 - Inflation-Deflation Episodes in the Hengill and Hrómundartindur Volcanic Complexes, SW Iceland

AU - Ducrocq, Cécile

AU - Geirsson, Halldór

AU - Árnadóttir, Þóra

AU - Juncu, Daniel

AU - Drouin, Vincent

AU - Gunnarsson, Gunnar

AU - Kristjánsson, Bjarni R.

AU - Sigmundsson, Freysteinn

AU - Hreinsdóttir, Sigrún

AU - Tómasdóttir, Sigrún

AU - Blanck, Hanna

N1 - Funding Information: We are very thankful to Thorsteinn J?nsson, Sveinbj?rn Steinth?rsson and students for assistance in the GNSS data collection over the years. We acknowledge UNAVCO and National Land Survey of Iceland for sharing their GNSS equipments. We are grateful to the National Land Survey of Iceland and Iceland GeoSurvey for sharing of their GNSS campaign data sets. We extend the gratitude to Benedikt G. ?feigsson and Icelandic Meteorological Office for the maintenance of continuous GNSS stations. We are thankful to the Copernicus and European Space Agency for the free access data sets of Sentinel-1. We fully acknowledge the satellite data sets provided by the German Aerospace Center used in the study: the TanDEM-X DEM (project IDEM_GEOL0123) and TerraSAR-X images provided through the Icelandic Volcanoes Supersite project (http://geo-gsnl.org/supersites/permanent-supersites/iceland-volcanoes-supersite/) through the Committee on Earth and Observing Satellites (CEOS). Most of the figures were created using the GMT software v.6.0.0 (Wessel et al., 2019). The high resolution digital elevation model used in Figure 1 is derived from the Arctic DEM (Porter et al., 2018) modified by the National LandSurvey of Iceland (2020). Comments on the drafts from Gu?finna Th. A?algeirsd?ttir (University of Iceland) were particularly appreciated. We thank two reviewers for their comments and suggestions which improved the manuscript. Funding Information: This work was funded via the Icelandic Research Fund, grant 174377-015 and NordVulk fellowship programme 2020. Publisher Copyright: © Copyright © 2021 Ducrocq, Geirsson, Árnadóttir, Juncu, Drouin, Gunnarsson, Kristjánsson, Sigmundsson, Hreinsdóttir, Tómasdóttir and Blanck.

PY - 2021/10/11

Y1 - 2021/10/11

N2 - Non-eruptive uplift and subsidence episodes remain a challenge for monitoring and hazard assessments in active volcanic systems worldwide. Sources of such deformation may relate to processes such as magma inflow and outflow, motion and phase changes of hydrothermal fluids or magma volatiles, heat transfer from magmatic bodies and heat-mining from geothermal extraction. The Hengill area, in southwest Iceland, hosts two active volcanic systems, Hengill and Hrómundartindur, and two high-temperature geothermal power plants, Hellisheiði and Nesjavellir. Using a combination of geodetic data sets (GNSS and InSAR; Global Navigation Satellite Systems and Interferometry Synthetic Aperture Radar, respectively) and a non-linear inversion scheme to estimate the optimal analytical model parameters, we investigate the ground deformation between 2017–2018. Due to other ongoing deformation processes in the area, such as plate motion, subsidence in the two geothermal production fields, and deep-seated source of contraction since 2006, we estimate 2017–2018 difference velocities by subtracting background deformation, determined from data spanning 2015–2017 (InSAR) or 2009–2017 (GNSS). This method highlights changes in ground deformation observed in 2017–2018 compared to prior years: uplift signal of ∼10 km diameter located in the eastern part of the Hengill area, and geothermal production-related temporal changes in deformation near Húsmúli, in the western part of the Hengill area. We find an inflation source located between the Hengill and Hrómundartindur volcanic complexes, lasting for ∼5 months, with a maximum uplift of ∼12 mm. Our model inversions give a source at depth of ∼6–7 km, located approximately in the same crustal volume as an inferred contracting source in 2006–2017, within the local brittle-ductile transition zone. No significant changes were observed in local seismicity, borehole temperatures and pressures during the uplift episode. These transient inflation and deflation sources are located ∼3 km NW from a source of non-eruptive uplift in the area (1993–1999). We consider possible magmatic and hydrothermal processes as the causes for these inflation-deflation episodes and conclude that further geophysical and geological studies are needed to better understand such episodes.

AB - Non-eruptive uplift and subsidence episodes remain a challenge for monitoring and hazard assessments in active volcanic systems worldwide. Sources of such deformation may relate to processes such as magma inflow and outflow, motion and phase changes of hydrothermal fluids or magma volatiles, heat transfer from magmatic bodies and heat-mining from geothermal extraction. The Hengill area, in southwest Iceland, hosts two active volcanic systems, Hengill and Hrómundartindur, and two high-temperature geothermal power plants, Hellisheiði and Nesjavellir. Using a combination of geodetic data sets (GNSS and InSAR; Global Navigation Satellite Systems and Interferometry Synthetic Aperture Radar, respectively) and a non-linear inversion scheme to estimate the optimal analytical model parameters, we investigate the ground deformation between 2017–2018. Due to other ongoing deformation processes in the area, such as plate motion, subsidence in the two geothermal production fields, and deep-seated source of contraction since 2006, we estimate 2017–2018 difference velocities by subtracting background deformation, determined from data spanning 2015–2017 (InSAR) or 2009–2017 (GNSS). This method highlights changes in ground deformation observed in 2017–2018 compared to prior years: uplift signal of ∼10 km diameter located in the eastern part of the Hengill area, and geothermal production-related temporal changes in deformation near Húsmúli, in the western part of the Hengill area. We find an inflation source located between the Hengill and Hrómundartindur volcanic complexes, lasting for ∼5 months, with a maximum uplift of ∼12 mm. Our model inversions give a source at depth of ∼6–7 km, located approximately in the same crustal volume as an inferred contracting source in 2006–2017, within the local brittle-ductile transition zone. No significant changes were observed in local seismicity, borehole temperatures and pressures during the uplift episode. These transient inflation and deflation sources are located ∼3 km NW from a source of non-eruptive uplift in the area (1993–1999). We consider possible magmatic and hydrothermal processes as the causes for these inflation-deflation episodes and conclude that further geophysical and geological studies are needed to better understand such episodes.

KW - joint inversion

KW - satellite geodesy

KW - time-series analysis

KW - volcano deformation

KW - volcano monitoring

UR - http://www.scopus.com/inward/record.url?scp=85117916711&partnerID=8YFLogxK

U2 - 10.3389/feart.2021.725109

DO - 10.3389/feart.2021.725109

M3 - Article

AN - SCOPUS:85117916711

SN - 2296-6463

VL - 9

JO - Frontiers in Earth Science

JF - Frontiers in Earth Science

M1 - 725109

ER -

Inflation-Deflation Episodes in the Hengill and Hrómundartindur Volcanic Complexes, SW Iceland

Abstract

Bibliographical note

Other keywords

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