1500 year old Eyjafjallajökull tephra

I´m off in to the field to track down the Layer H tephra (sometimes called E500) from Eyjafjallajökull. This is preliminary fieldwork for a new project trying to find out more about this prehistoric eruption of Eyjafjallajökull, in collaboration with Andrew Dugmore, Anthony Newton, Thorvaldur Thordarsson at the University of Edinburgh and Guðrún Larsen at University of Iceland.

So, after this fieldwork and a bit of lab work and analyses we should be able to:

• make an isopach map
• calculate deposit density and produce an isomass map
• estimate deposit volume and mass
• carry out grain size analyses of tephra samples
• estimate total grain size distribution from the deposit
• assess the size and explosivity of the eruption

We already have quite a lot of thickness data from my PhD research and Andy Dugmore´s decades of research in this area and good geochemical data so this new fieldwork and sample collection campaign will help us fill out some of the gaps in geographical coverage that we have just now and all us to make some interesting comparisons between this prehistoric eruption and the more recent eruptions of Eyjafjallajökull. Exciting stuff!!

Here´s hoping for good weather and some soils where I want to find them.

Tephra in Quaternary Science: Eyjafjallajökull 2010

5th to 6th May, 2011

Exciting: I am co-organising a workshop for the new Quaternary Research Association research group Tephra in Quaternary Science, with Prof. Andy Dugmore and Dr. Anthony Newton at the University of Edinburgh. With keynote talks from Thor Thordarson (University of Edinburgh) and Susan Leadbetter (UK Met Office) and a workshop summary from Sue Loughlin (British Geological Survey) and several discussion sessions these should be a really interesting couple of days. Many aspects of tephra to be covered: characterisation of deposits, proximal and distal deposition patterns, dispersal and modelling of tephra transport,.. and of course the Eyjafjallajökull eruptions themselves. Funding comes from INQUA and QRA and this is great because it means there doesn't have to be any registration fee and early career researchers and postgrads can be supported in their attendance. :) Looking forward to some lively discussions, a friendly few days and learning a lot.

Edinburgh Visiting Fellow

I am now based in Edinburgh and am a visiting fellow in Geography at the University of Edinburgh while still maintaining my affiliation with the University of Iceland. I can still be contacted at kate@raunvis.hi.is.

Hazard mapping news

Freysteinn Sigmundsson, Erik Sturkell and I presented preliminary results of our hazard mapping project for Snæfellsjökull at the Natural Science Symposium (Raunvísindaþing) in Reykjavík in March. Have a look here for the abstract and here for an image of the poster. Feel free to contact me for more information or for a pdf file of the poster which should be clearer.

In May we (Freysteinn, Ármann Sigmundsson and I) begin a new project, funded by Landsvirkjun, modeling tephra fallout from Hekla. This will involve collating information of past eruptive and weather conditions during activity at Hekla and resultant tephra fall patterns and characteristics. We will combine this information in a GIS system, as we have done for volcanic phenomena at Snæfellsjökull, and carry out modeling of tephra fallout and sedimentation patterns. I am impressed with how useful it has been to use a GIS system to combine and analyse spatial as well as temporal data in these hazard mapping projects and look forward to applying process-related modeling to further tailor our hazard assessments to specific eruptions scenarios, which we intend will make them much easier to interpret and understand in the event of a future eruption.

Palaeoenvironmental reconstruction as a tool in hazard assessment: a case study at Snæfellsjökull

K. T. Smith, F. Sigmundsson and E. Sturkell 2008. Palaeoenvironmental reconstruction as a tool in hazard assessment: a case study at Snæfellsjökull. Poster presented at the Natural Science Symposium, University of Iceland, Reykjavík, March 2008.

Click on this here, and then again on the small poster image, for a larger jpg image of the poster.

Abstract

Here we present the results of recent palaeoenvironmental reconstructive work carried out with the aim of assessing hazard and risk from Snæfellsjökull volcano and a discussion of both the value and limitations of this approach in assessing hazard and risk.

This research aimed to assess multiple volcanic hazards at Snællsjökull by collating past work on volcanic history and augmenting this with new data collected in this project, and presented here, on volcanic floods (jökulhlaups) / lahars and tephra fall. Geomorphological and sedimentological evidence indicates that relatively small flood or lahar events have radiated from the volcano carrying pumice, most likely at or shortly after the time of major eruptions. In addition, sedimentological investigations of tephra deposition agree with past studies that showed that the main axis of tephra fall was to the east north east. Deposition of tephra from central volcanic eruptions was also found to the south and west, as were localised tephrafalls from smaller flank craters. It is clear from this study that tephra fall thickness rapidly diminished with distance from the source vent of major eruptions with over one metre of tephra found close to the present ice margin and less than 10 cm on the lower slopes of the volcano, even along the axis of deposition. Holocene lava flows [1] are primarily found to the west and south of the main volcano and from small cones on the surrounding lowlands. This work indicates that the most hazardous and widespread volcanic phenomenon likely to come from Snæfellsjökull is tephrafall, with limited hazard from floods and lava flows. However, questions remain about events common at stratovolcanoes (e.g. Öræfajökull) such as pyroclastic flows, of which no clear palaeoenvironmental evidence has yet been found at Snæfellsjökull.

This approach of basing hazard mapping on palaeoenvironmental and geological data is used throughout the world to assess volcanic hazards and it gives a excellent generalised view of how specific volcanic phenomenon may behave based on past activity and on rules definied by physical factors such as topography (e.g. flows will flow downhill and follow drainage routes). However, the useability and fullness of the results of such a project depend very much on the degree of preservation of palaeoenvironmental evidence, as well as the extent to which available resources will allow gaps in existing knowledge to be filled.

The distribution and impact of volcanic products and processes dependents upon topography, source location and meteorological conditions as well as the nature of the eruption. Consequently, there is a need for further investigation of specific past volcanic events of which little is yet known and modelling of specific likely future scenarios to develop a scenario-specific hazard and risk assessment for multiple hazards around volcanoes, including at Snæfellsjökull.

References:
[1] H. Jóhannesson, Lava flow map, produced for Snæfellsjökull National Park (Reykjavík) (pers. comm. 2005)