Skip to content

New evidence for prolonged ash emission during silicic eruptions in Iceland

Jingwei Zhang1, Hugh Tuffen1, Fabian B. Wadsworth2, Jamie Farquharson3, Holly Unwin4, Dave McGarvie1, Daníel Freyr Jónsson5

  • Affiliations: ^ 1^Lancaster Environment Centre, Lancaster University, Lancaster, UK;  2Department of Earth and Environmental Sciences, Ludwig-Maximilians-Univeristät München, Munich, Germany; 3Niigata University, Niigata, Japan; 4British Geological Survey, UK; 5Environment Agency of Iceland, Iceland

  • Presentation type: Poster

  • Presentation time: Friday 16:30 - 18:00, Room Poster Hall

  • Poster Board Number: 157

  • Programme No: 3.4.33

  • Theme 3 > Session 4

Abstract

There is increasing evidence that the apparently effusive phase of silicic eruptions may be hybrid in style - including sustained ash emissions alongside lava emplacement. However, the prevalence of hybrid activity in past events remains unknown and is little documented. Recently recognized features that are diagnostic of hybrid activity are veneers of welded ash found on lava fracture surfaces. We show that these veneers are present on all Holocene rhyolitic lavas of Torfajökull volcano, Iceland. We focus on lavas of the 877 CE Hrafntinnuhraun eruption and show that such ash veneers present in all of its flow units are texturally comparable to those described from Cordon Caulle, indicating that similar ash venting likely took place throughout the entire lava- producing phase of the Hrafntinnuhraun eruption. We construct a simple first-order model for the rates of ash capture by veneer surfaces and upscale this calculation to the whole eruption, allowing us to estimate the total ash mass that can be sequestered. We posit that such hybrid explosive-effusive activity is common to silicic volcanism in general and that it represents an insufficiently recognized hazard.