Effects of Glaciation on Volcanism in Iceland

Volcanic eruption rates in Iceland during the last deglaciation increased 5--30 fold from the steady-state rates. This has been understood by the unloading of ice, which increases the decompression rates in the mantle, causing enhanced mantle melting rates. However, existing theoretical work cannot...

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Main Author: Eksinchol, Isarapong
Format: Thesis
Language:English
Published: Apollo - University of Cambridge Repository 2019
Subjects:
Online Access:https://dx.doi.org/10.17863/cam.44709
https://www.repository.cam.ac.uk/handle/1810/297655
id ftdatacite:10.17863/cam.44709
record_format openpolar
spelling ftdatacite:10.17863/cam.44709 2023-05-15T16:46:50+02:00 Effects of Glaciation on Volcanism in Iceland Eksinchol, Isarapong 2019 https://dx.doi.org/10.17863/cam.44709 https://www.repository.cam.ac.uk/handle/1810/297655 en eng Apollo - University of Cambridge Repository https://www.rioxx.net/licenses/all-rights-reserved/ All Rights Reserved All rights reserved Iceland Mid-Ocean Ridge Volcanism Glaciation Geophysics FOS Earth and related environmental sciences Mantle Flow Mantle Melting Magmatism Rare Earth Elements Deglaciation Melt Transport Melt Ascent Velocity Forcasting Last Deglaciation Numerical Modelling Subglacial Postglacial Lavas Text Thesis article-journal ScholarlyArticle 2019 ftdatacite https://doi.org/10.17863/cam.44709 2021-11-05T12:55:41Z Volcanic eruption rates in Iceland during the last deglaciation increased 5--30 fold from the steady-state rates. This has been understood by the unloading of ice, which increases the decompression rates in the mantle, causing enhanced mantle melting rates. However, existing theoretical work cannot account for large variations of Rare Earth Element (REE) concentrations in the Icelandic lavas. Lavas erupted during the last deglaciation are depleted in REEs by up to 70\%; whereas, existing models can only produce at most 20\% depletion. This dissertation attempts to find the causes of this mismatch and provides the first models that take account of the diachronous response of volcanism to deglaciation. Numerical models of mantle flow and mantle melting response to the glaciation and deglaciation are developed. A time-lag sampler is incorporated to represent the time lag between the melt production at depths and the eruption on the Earth's surface due to finite rate of melt transport. The model results for the last deglaciation in Iceland show that the variations of REE concentrations are strongly dependent on the melt ascent velocity. This explains the REE concentration mismatch between the previous theoretical work and the observations. Comparison between the model results (timing of the bursts in volcanic eruptions, REE concentration variations, and volume proportions of the subglacial, finiglacial and postglacial eruptions) and the observational data suggests that the melt ascent velocity during the last deglaciation beneath Iceland is of the order of $\sim$100~$\text{m/year}$. The effects of glacial loading during the last glacial period on mantle melting are also investigated. It is found that glacial loading suppresses mantle melting and modulates the average REE concentrations in the melts due to the depth-dependent profile of mantle melting suppression. In addition, this dissertation explores how different deglaciation histories can result in different REE concentrations in the early-postglacial lavas. This may explain why lava shields formed during the Termination~II have different geochemical compositions from that formed during the Termination~I. Lastly, predictions for the future of the Icelandic volcanic eruption rates are made based on given estimated deglaciation rates of the current Icelandic glaciers. : Cambridge Trust and Leverhulme Trust Thesis Iceland DataCite Metadata Store (German National Library of Science and Technology)
institution Open Polar
collection DataCite Metadata Store (German National Library of Science and Technology)
op_collection_id ftdatacite
language English
topic Iceland
Mid-Ocean Ridge
Volcanism
Glaciation
Geophysics
FOS Earth and related environmental sciences
Mantle Flow
Mantle Melting
Magmatism
Rare Earth Elements
Deglaciation
Melt Transport
Melt Ascent Velocity
Forcasting
Last Deglaciation
Numerical Modelling
Subglacial
Postglacial
Lavas
spellingShingle Iceland
Mid-Ocean Ridge
Volcanism
Glaciation
Geophysics
FOS Earth and related environmental sciences
Mantle Flow
Mantle Melting
Magmatism
Rare Earth Elements
Deglaciation
Melt Transport
Melt Ascent Velocity
Forcasting
Last Deglaciation
Numerical Modelling
Subglacial
Postglacial
Lavas
Eksinchol, Isarapong
Effects of Glaciation on Volcanism in Iceland
topic_facet Iceland
Mid-Ocean Ridge
Volcanism
Glaciation
Geophysics
FOS Earth and related environmental sciences
Mantle Flow
Mantle Melting
Magmatism
Rare Earth Elements
Deglaciation
Melt Transport
Melt Ascent Velocity
Forcasting
Last Deglaciation
Numerical Modelling
Subglacial
Postglacial
Lavas
description Volcanic eruption rates in Iceland during the last deglaciation increased 5--30 fold from the steady-state rates. This has been understood by the unloading of ice, which increases the decompression rates in the mantle, causing enhanced mantle melting rates. However, existing theoretical work cannot account for large variations of Rare Earth Element (REE) concentrations in the Icelandic lavas. Lavas erupted during the last deglaciation are depleted in REEs by up to 70\%; whereas, existing models can only produce at most 20\% depletion. This dissertation attempts to find the causes of this mismatch and provides the first models that take account of the diachronous response of volcanism to deglaciation. Numerical models of mantle flow and mantle melting response to the glaciation and deglaciation are developed. A time-lag sampler is incorporated to represent the time lag between the melt production at depths and the eruption on the Earth's surface due to finite rate of melt transport. The model results for the last deglaciation in Iceland show that the variations of REE concentrations are strongly dependent on the melt ascent velocity. This explains the REE concentration mismatch between the previous theoretical work and the observations. Comparison between the model results (timing of the bursts in volcanic eruptions, REE concentration variations, and volume proportions of the subglacial, finiglacial and postglacial eruptions) and the observational data suggests that the melt ascent velocity during the last deglaciation beneath Iceland is of the order of $\sim$100~$\text{m/year}$. The effects of glacial loading during the last glacial period on mantle melting are also investigated. It is found that glacial loading suppresses mantle melting and modulates the average REE concentrations in the melts due to the depth-dependent profile of mantle melting suppression. In addition, this dissertation explores how different deglaciation histories can result in different REE concentrations in the early-postglacial lavas. This may explain why lava shields formed during the Termination~II have different geochemical compositions from that formed during the Termination~I. Lastly, predictions for the future of the Icelandic volcanic eruption rates are made based on given estimated deglaciation rates of the current Icelandic glaciers. : Cambridge Trust and Leverhulme Trust
format Thesis
author Eksinchol, Isarapong
author_facet Eksinchol, Isarapong
author_sort Eksinchol, Isarapong
title Effects of Glaciation on Volcanism in Iceland
title_short Effects of Glaciation on Volcanism in Iceland
title_full Effects of Glaciation on Volcanism in Iceland
title_fullStr Effects of Glaciation on Volcanism in Iceland
title_full_unstemmed Effects of Glaciation on Volcanism in Iceland
title_sort effects of glaciation on volcanism in iceland
publisher Apollo - University of Cambridge Repository
publishDate 2019
url https://dx.doi.org/10.17863/cam.44709
https://www.repository.cam.ac.uk/handle/1810/297655
genre Iceland
genre_facet Iceland
op_rights https://www.rioxx.net/licenses/all-rights-reserved/
All Rights Reserved
All rights reserved
op_doi https://doi.org/10.17863/cam.44709
_version_ 1766036931997597696