The interaction of subglacial volcanoes and their overlying ice cover is characterised by large-scale floods, jökulhlaups, carrying sediment, fresh volcanogenic material and ice.
Öræfajökull (highest peak 2119 m, 13 peaks higher than 1500 m) is a steep, ice-covered cone which has erupted twice since
Snæfellsjökull, like Öræfajökull and Eyjafjallajökull, is a high ice-capped cone (1446 m) rising up from sea level with a 200 m deep summit crater completely infilled with ice. Three eruptions are known of in the Holocene, the most recent around 1750 radiocarbon years ago produced lava and tephra-fall. Snæfellsjökull is the central focus of a national park, a popular tourist location within sight of Reykjavík. Should a flood occur here in the future, the communities and tourist centres throughout the national park, several farms, airfields, the main road and bridges may all be within the most hazardous regions.
The aim of this research is to reconstruct past flood/flow events in
- Determine if Snæfellsjökull has been subject to volcanic flood activity or rain-triggered lahars during the Holocene.
- If so, map and produce a chronology of these events.
- Produce a hazard map of zones of inundation and risk.
- Produce a tephrochronological framework in which to place this environmental record.
Particularly thick (more than 5 metres high) deposits are found close to the ice margins, and overlying glacial ice-marginal landforms to the north and east of the volcano. It is as yet unclear if these are primary airfall deposits or flood deposits.
Geomorphological mapping, preliminary sedimentary investigations carried out since the summer of 2005 and points noted by Jóhannesson and others (2001) during tephrochronological studies indicate that there have in the past been at least three main flood routes associated with eruptions. Pumice left by tephra fall and jökulhlaup deposition during the last eruption is found in very thick deposits close to the northern and eastern contemporary glacial limits. As well as eruption-related jökulhlaups the presence of these thick, light-weight, unconsolidated deposits could have resulted in an extended period of rain-triggered reworking of material in lahars and damming of drainage routes by accumulations of erupted and flood-deposited material.
Jóhannesson, H., Flores, R. M. and Jónsson, J. 1981. A short account of the Holocene tephrochronology of the Snæfellsjökull central volcano, Western Iceland. Jökull, 31, 23-30.
K.T.Smith (2006) ´Jökulhlaups from Snæfellsjökull, west Iceland´ IGS International Symposium on Earth and Planetary Ice-Volcano Interactions, Reykjavík, Iceland. 19th - 23rd June 2006, Abstract volume, Abstract no: 45A049.