The Open UniversitySkip to content
 

The AD 1362 Öræfajökull eruption, S.E. Iceland: Physical volcanology and volatile release

Sharma, Kirti; Self, Stephen; Blake, Stephen; Thordarson, Thorvaldur and Larsen, Gudrun (2008). The AD 1362 Öræfajökull eruption, S.E. Iceland: Physical volcanology and volatile release. Journal of Volcanology and Geothermal Research, 178(4) pp. 719–739.

DOI (Digital Object Identifier) Link: http://dx.doi.org/10.1016/j.jvolgeores.2008.08.003
Google Scholar: Look up in Google Scholar

Abstract

The explosive rhyolitic eruption of Öræfajökull volcano, Iceland, in AD 1362 is described and interpreted based on the sequence of pyroclastic fall and flow deposits at 10 proximal locations around the south side of the volcano. Öræfajökull is an ice-clad stratovolcano in south central Iceland which has an ice-filled caldera (4–5 km diameter) of uncertain origin. The main phase of the eruption took place over a few days in June and proceeded in three main phases that produced widely dispersed fallout deposits and a pyroclastic flow deposit. An initial phase of phreatomagmatic eruptive activity produced a volumetrically minor, coarse ash fall deposit (unit A) with a bi-lobate dispersal. This was followed by a second phreatomagmatic, possibly phreatoplinian, phase that deposited more fine ash beds (unit B), dispersed to the SSE. Phases A and B were followed by an intense, climactic Plinian phase that lasted 8–12 h and produced unit C, a coarse-lapilli, pumice-clast-dominated fall deposit in the proximal region. At the end of Plinian activity, pyroclastic flows formed a poorly-sorted deposit, unit D, presently of very limited thickness and exposed distribution. Much of Eastern Iceland is covered with a very fine distal ash layer, dispersed to the NE. This was probably deposited from an umbrella cloud and is the distal representation of the Plinian fallout. A total bulk fall deposit volume of 2.3 km3 is calculated ( 1.2 km3 DRE). Pyroclastic flow deposit volumes have been crudely estimated to be < 0.1 km3. Maximum clast size data interpreted by 1-D models suggests an eruption column 30 km high and mass discharge rates of 108 kg s− 1. Ash fall may have taken place from heights around 15 km, above the local tropopause ( 10 km), with coarser clasts dispersed below that under a different wind regime. Analyses of glass inclusions and matrix glasses suggest that the syn-eruptive SO2 release was only 1 Mt. This result is supported by published Greenland ice-core acidity peak data that also suggest very minor sulphate deposition and thus SO2 release. The small sulphur release reflects the low sulphur solubility in the 1362 rhyolitic melt. The low tropopause over Iceland and the 30-km-high eruption column certainly led to stratospheric injection of gas and ash but little sulphate aerosol was generated. Moreover, pre-eruptive and degassed halogen concentrations (Cl, F) indicate that these volatiles were not efficiently released during the eruption. Besides the local pyroclastic flow (and related lahar) hazard, the impact of the Öræfajökull 1362 eruption was perhaps restricted to widespread ash fall across Eastern Iceland and parts of northern Europe.

Item Type: Journal Article
Copyright Holders: 2008 Elsevier B.V.
ISSN: 0377-0273
Academic Unit/Department: Other Departments > Other Departments
Science > Environment, Earth and Ecosystems
Interdisciplinary Research Centre: Centre for Earth, Planetary, Space and Astronomical Research (CEPSAR)
Item ID: 12911
Depositing User: Stephen Blake
Date Deposited: 28 Jan 2009 01:40
Last Modified: 23 Oct 2012 14:40
URI: http://oro.open.ac.uk/id/eprint/12911
Share this page:

Actions (login may be required)

View Item
Report issue / request change

Policies | Disclaimer

© The Open University   + 44 (0)870 333 4340   general-enquiries@open.ac.uk