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.


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.

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