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| Titel |
Variations in geothermal heat flux at Grímsvötn, Iceland |
| VerfasserIn |
Hannah Iona Reynolds, Magnus Tumi Gudmundsson |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250089953
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| Publikation (Nr.) |
 EGU/EGU2014-4462.pdf |
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| Zusammenfassung |
| Thermal signals from sub-surface magmatic sources are difficult to quantify, as the
measurement of fluxes from the ground to the atmosphere is subject to large uncertainties.
Ice cauldrons are depressions which form on the surface of glaciers due to basal
melting as a result of geothermal flux from the bedrock beneath, often generated by
volcanic sources. The monitoring of ice cauldrons provides a unique opportunity
to quantify heat flux to a much improved accuracy, as the melting ice acts as a
calorimeter.
Time series data of ice surface elevation at cauldrons above Grímsvötn volcano are
presented over a 14 year period, with estimates of the melt volume and surface heat flux
required for this melting to have occurred. Three volcanic eruptions took place at Grímsvötn
during the study period, the effects of which are visible in ice surface elevation data.
However, separate thermal anomalies are observed in areas unaffected by erupted products. A
peak in surface heat flux is observed following the 1998 eruption, several kilometres
east of the vent, with a maximum rise of ~200 W-
m-2. The anomalous signal
lasts for approximately three years. Possible explanations include the intrusion of a
dyke beneath this area during the eruption, or increased permeability from greater
dilatational strain due to regional stress, both of which would significantly increase heat
flux.
We investigate possible scenarios which could produce such a thermal anomaly, using
finite element modelling. The effects of cooling magmatic intrusions and changes to the
parameter space for country rock conductivity and permeability are considered, in relation to
heat flux and the timescales and spatial extent of associated surface anomalies. Our results
advance the understanding and interpretation of thermal signals observed at ice-covered
volcanoes. |
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