Háskóli Íslands

ESPSI

ESPSI

Verkefnanúmer: 750733
Styrkur í samræmi við: H2020-EU.1.3.2. - Nurturing excellence by means of cross-border and cross-sector mobility

Eruption Source Parameters for Explosive Eruptions in Iceland Over the Last 3 ka

Upphafsdagur / Start date

Lokadagur / Final date

Staða / Status

15. júní 2017

14. júní 2019

Final report submitted

Um verkefnið:

Heildarkostnaður / Total cost

EUR 179.325,60

Viðfangsefni:
MSCA-IF-2016 - Individual Fellowships

Heildarstyrkur / Total grant
EUR 179.325,60

Styrkur sóttur í: 
H2020-MSCA-IF-2016

Stýrt af / coordinated by:
Háskóli Íslands

Tegund styrk / Type of grant
MSCA-IF-EF-ST - Standard EF
 

Nánari upplýsingar um verkefnið má finna hér.

Markmið / Objectives

Eruption source parameters (ESPs)—such as erupted volume/mass, plume height, magma discharge, tephra dispersal, and total grain size distribution (TDGS)—are key information for characterizing explosive eruptions and essential input parameters in tephra dispersal models used for real-time forecasting by the Volcanic Ash Advisory Centers (VAACs) and for long-term hazard assessments. Iceland is one of the volcanically most active regions of the world, with over 20 events per century. About ~700 events are preserved in the post-glacial soil and lake sediments in Iceland. ESPs, however, have yet to be determined for most of the eruptions. ESPs are traditionally derived using empirical approaches, requiring detailed field measurements of the deposits. The objective of this action is to estimate, to the first order, the ESPs for explosive eruptions in Iceland using inversion modelling. The advantage of this approach is that it bypasses the compilation of detailed isopach maps through the use of optimization algorithms. It requires only a limited number of thickness measurements and grain size analyses. Consequently, ESPs can be established for a larger number of eruptions in a shorter time, than when using traditional empirical methods. This will result in a statistically robust data set on ESPs used for determining the magnitude a nd intensities of explosive eruptions in Iceland as well as for assessing risk and mitigating hazards associated with such events.

Iceland is one of the volcanically most active regions of the world, with over 20 eruptions per century and a majority (>70%) feature significant explosive activity. About 700 tephra-producing events are preserved in the post-glacial soil and lake sediments in Iceland and the portions representing the last 3 ka contain about 200–250 events. Eruption Source Parameters (ESPs)—namely eruption duration, erupted volume/mass, plume height, magma discharge rate, and total grain size distribution— have yet to be determined for most of these eruptions. ESPs are traditionally derived from field measurements via a range of empirical methods. A common feature of all these approaches is that they require detailed mapping of the tephra deposits, which is very time consuming and expensive in terms of man hours. 

The principal objectives of this project were to (a) evaluate how effective inversion modelling of the tephra fallout from explosive eruptions is in estimating, to the first order, the range of ESPs for such event in Iceland and (b) correlate the tephra fall record, as preserved in lake sediment archives, in Western Iceland over the last 3 ka. The advantage of using inversion to reconstruct the ESPs for single eruptions is that it reduced the number of data points required for the reconstruction (i.e. saves time and cost) and thus bypasses the compilation of isopach maps, through optimization algorithms. Inversion is also very useful when there are not enough data points to construct precise isopach maps, but the dispersal axis is somewhat constrained.

This study focused on the tephra record over the last 3 ka from Hekla and Katla volcanoes. The chosen time period encompasses an estimated 160 eruptive events, thereof about 70 from Hekla and 90 from Katla. The targeted volcanoes are two of the three greatest tephra-producing volcanoes in Iceland. The post-3 ka activity at Hekla is a good representation of felsic (andesite to rhyolite) eruptions, while Katla activity is typified by explosive basaltic events. The aim of the project was to further the understanding of 1) the range of ESPs for the explosive eruptions produced by Hekla and Katla in the last 3 ka, 2) the ESPs for the most common explosive eruptions from  Hekla and Katla, and 3) the ESPs of the most extreme events and how often they occur. 

ESPs are key information for characterizing explosive eruptions, important input parameters in computer models used for real-time ash dispersal forecasting by the Volcanic Ash Advisory Centres and can also be used in hazard assessments. Hence, establishing a statistically robust data set of ESPs, for a small but representative subset of the explosive eruptions in Iceland is a critical task for both fundamental understanding of eruptive processes and for ash forecasting.

Isomass map of computed tephra accumulation (kg m-2) for the Hekla Z eruption. Orange triangle shows the inferred vent location, glaciers are shown in white, and rivers and lakes in blue. Locations used as input for the TEPHRA2 inversion are shown as black dots. 

Isomass map of computed tephra accumulation (kg m-2) for the Katla 1721 eruption. Orange triangle shows the inferred vent location, glaciers are shown in white, and rivers and lakes in blue. Locations used as input for the TEPHRA2 inversion are shown as black dots. 

Isomass maps of computed tephra accumulation (kg m-2) for the Katla 1918 eruption, modelled as three sectors. Orange triangle shows the inferred vent location, glaciers are shown in white, and rivers and lakes in blue. Locations used as input for the TEPHRA2 inversion are shown as black dots. 

 

Verkefnastýring (e. Coordinator)

Háskóli Íslands (UoI)                                                              Iceland

Þátttakendur / Personell involved:

Main reseracher in the project is:  Maria Helena Janebo, Post doctoral reseracher at the School of Engineering and Natural Sciences.  janebo[at] hi.is

The supervisor of the project at the University of ICeland is: Þorvaldur Þórðarsson , Professor in Volcanology and Petrology at the School of Engineering and Natural Sciences.

Publications

At least two publications in international, peer-reviewed journals under open access are still planned; one or two focusing on the results of the inversion modelling, and one on the tephra correlation/eruption frequency.

Styrkþegar / grant holder:

Háskóli Íslands

Iceland

 

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