Lava field evolution and emplacement dynamics of the 2014–2015 basaltic fissure eruption at Holuhraun, Iceland

Abstract

The 6-month long eruption at Holuhraun (August 2014-February 2015) in the Bárðarbunga-Veiðivötn volcanic system was the largest effusive eruption in Iceland since the 1783-1784 CE Laki eruption. The lava flow field covered~84 km 2 and has an estimated bulk (i.e., including vesicles) volume of~1.44 km 3. The eruption had an average discharge rate of~90 m 3 /s making it the longest effusive eruption in modern times to sustain such high average flux. The first phase of the eruption (August 31, 2014 to mid-October 2014) had a discharge rate of~350 to 100 m 3 /s and was typified by lava transport via open channels and the formation of four lava flows, no. 1-4, which were emplaced side by side. The eruption began on a 1.8 km long fissure, feeding partly incandescent sheets of slabby pāhoehoe up to 500 m wide. By the following day the lava transport got confined to open channels and the dominant lava morphology changed to rubbly pāhoehoe and 'a'ā. The latter became the dominating morphology of lava flows no. 1-8. The second phase of the eruption (Mid-October to end November) had a discharge of~100-50 m 3 /s. During this time the lava transport system changed, via the formation of a b 1 km 2 lava pond~1 km east of the vent. The pond most likely formed in a topographical low created by a the pre-existing Holuhraun and the new Holuhraun lava flow fields. This pond became the main point of lava distribution, controlling the emplacement of subsequent flows (i.e. no. 5-8). Towards the end of this phase inflation plateaus developed in lava flow no. 1. These inflation plateaus were the surface manifestation of a growing lava tube system, which formed as lava ponded in the open lava channels creating sufficient lavastatic pressure in the fluid lava to lift the roof of the lava channels. This allowed new lava into the previously active lava channel lifting the channel roof via inflation. The final (third) phase, lasting from December to end-February 2015 had a mean discharge rate of~50 m 3 /s. In this phase the lava transport was mainly confined to lava tubes within lava flows no. 1-2, which fed breakouts that resurfaced N 19 km 2 of the flow field. The primary lava morphology from this phase was spiny pāhoehoe, which superimposed on the 'a'ā lava flows no. 1-3 and extended the entire length of the flow field (i.e. 17 km). This made the 2014-2015 Holuhraun a paired flow field, where both lava morphologies had similar length. We suggest that the similar length is a consequence of the pāhoehoe is fed from the tube system utilizing the existing 'a'ā lava channels, and thereby are controlled by the initial length of the 'a'ā flows.

TanDEM‐X Time Series Analysis Reveals Lava Flow Volume and Effusion Rates of the 2012–2013 Tolbachik, Kamchatka Fissure Eruption

“…A more recent example is the 2014–2015 Holuhraun eruption of the Bardarbunga volcanic system in Iceland. Pedersen et al () discriminate between three different phases for the 6 month long eruption. The first phase lasted for 1.5 months and showed discharge rates between ∼350 to 100 m 3 /s.…”

Extended SO2 outgassing from the 2014–2015 Holuhraun lava flow field, Iceland

“…They observed that the majority of sulphur was released soon after eruption (60% was lost during flow over a distance of 12 km), but lava flows were observed to continue outgassing for at least 2 to 4 h after solidification (Swanson and Fabbi, 1973). In contrast, the Holuhraun lava flow field exhibits a wide range of lava morphologies, varying from pāhoehoe to 'a'ā (Pedersen et al 2017) and, as demonstrated by this work, continued to release sulphur volatiles for several months after emplacement.…”

“…where σ is the Stefan-Boltzmann constant (5.67051 × 10 −8 W/ m 2 /K 4 ), ε is the emissivity of the lava surface (assumed to be 0.95 for basalt; Patrick et al 2004), A flow is the final area of the cooling lava flow field (84 km 2 ; Pedersen et al 2017), and BT MIR,flow and BT MIR,bk are the average brightness temperatures of the flow surface pixels and surrounding background, respectively, calculated from selected MODIS-MIROVA cloud-free images (Fig. 6).…”

Hekla Volcano, Iceland, in the 20th Century: Lava Volumes, Production Rates, and Effusion Rates

“…The total eruption volume from Hekla volcano in the 20th century is larger than any other Icelandic central volcanoes and is similar in size to the 6 month Holuhraun eruption in 2014-2015 (Pedersen et al, 2017). However, rates of higher productivity have been observed over shorter time periods, for example, during the Krafla fires (Harris et al, 2000).…”