Emplacement and Growth of the August 2014 to February 2015 Nornahraun Lava Flow Field North Iceland

Abstract:

The 31.08.2014 to 27.02.2015 Nornahraun eruption in North Iceland is the largest eruption in Iceland in 232 years, producing an 85km² lava flow field with a volume of 1.5-2km³. The eruption began on a 2 km long fissure that cut through the 1797AD Holuhraun vent system, spreading lava onto the flat (slope <0.4°) Dyngjujokull outwash plane. At mean magma discharge of 250 m³  the lava was transported from the vents via a 3.5km long lava channel, feeding a 1–2km wide rubbly pāhoehoe to ‘a‘a flow front advancing to the NE at rate of 1–2 km/day. This lava flow came to halt on 12 September at a distance of 18km from the vents and for the next 5 days it was subjected to endogenous growth reaching a mean thickness 12m and a volume 0.35km³. Mean magma discharge dropped to 150 m³/s on 18^th and the vent activity was reduced to a 500 m long central segment of the fissure. A new lava flow formed, advancing along the southern margins of the first, coming to rest on 22 September at 11.5 km from the vents (vol. 0.09km³). On 23^rd the third flow formed, advanced along south and north margins of the flow field, reaching a maximum length of 6.7 km as it came to rest on the 26^th (vol. 0.06km³). Increase in magma discharge to about 220 m³/s is observed between 27 September and 8 October forming the 4^th lava flow along the south margins of the flow field. This flow surged out to a distance of 15km in 12 days (vol. 0.22km³). Flow 5 formed between 9 to 30 October at mean discharge of 140 m³/s, advancing along the south side of flow 4 and reaching length of 11 km (vol. 0.30km³). Similarly, the sixth flow formed along flow 5 between 1-14 November at mean discharge of 110 m³/s and reaching length of 7.5km (vol. 0.11km³). This signaled the end of this gradual clockwise widening of the flow field, which coincided with partial crusting over of the lava channel and initiation of insulated flows that were emplaced on top of the earlier formed flows for the reminder of the eruption.