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.
Showing posts with label Conference abstracts. Show all posts
Showing posts with label Conference abstracts. Show all posts
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.
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)
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)
Volcanogenic hazards and resultant risks to road systems and infrastructure: preliminary assessments at Snæfellsjökullsearch workshop
Kate Smith
Jarðvísindastofnun Háskolans, Askja, Sturlugata 7, 101 Reykjavík.
Snæfellsjökull is a high ice-capped volcanic cone (1446 m) rising up from sea level to a 200 m deep summit crater infilled with ice. Three major phreatic (plinian) eruptions are understood to have occurred in the Holocene, the most recent being around 1855 radiocarbon years ago. Geological mapping indicates that over 25 eruptions have occurred in the Snæfellsjökull central volcano in the last 10,000 years producing lava, tephra and jökulhlaup or lahar events. Pyroclastic flows and wave (small-scale “tsunami”) effects may be likely events in a future eruption although no evidence of these has yet been identified in the geological record. Snæfellsjökull is the central focus of a national park and therefore a major travel destination. The communities of Snæfellsbær are home year-round to 1717 people, increasing dramatically during the main summer travelling season and at weekends. As we know from Öræfajökull, the eruptions of relatively infrequently erupting stratovolcanoes can be dramatic and are worthy of assessment. Should an eruption occur here in the future, nearby communities throughout the national park, several farms, airfields, the main road and bridges may be within the most hazardous regions and the impacts of tephrafall and wave effects may be felt much farther afield.
Although excellent hazard maps exist in
New research supported by Vegagerðin over the last two years has focussed on the nature and distribution of floods/lahars and tephrafall from Snæfellsjökull. Floods/lahars have flowed in many directions from Snæfellsjökull, primarily carrying pumice clasts. These floods were relatively small in comparison with historical Katla and Grímsvötn floods due to the smaller icecap and the numerous directions of flow. Tephra distribution studies back up past studies showing that the main zone of deposition was to the east north east although evidence has now been found to show that tephrafall did also occur to the west and south of the volcano. 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. There is therefore variable probability of each of these events in different areas of the district and resultant variability in risk to infrastructure including roads.
Here we compile what we know about past events at Snæfellsjökull and present preliminary considerations of how this translates into hazard and risk for the district and particularly for the road system. This project aims to produce hazard maps in a manner suitable for use by a wide variety of individuals and organisations. Such maps combined with an assessment of vulnerability can be used to determine risk and to enable risk-reduction measures to be taken if required. Emphasis is placed on hazard and risk for road systems since the road network is one of the most important means of evacuation and communication and the restoration and maintenance of other lifelines depend on the movement of people and equipment to sites impacted/damaged by volcanic events.
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