InSAR-derived Thermoelastic Lava Flow Compaction Following the 2014/15 Holuhraun Fissure Eruption

Abstract:

The Icelandic volcano Bárðarbunga experienced a caldera collapse and fissure eruption at Holuhraun from August 16, 2014 to February 27, 2015. This eruption produced about 1.5 km³ of lava, which is the largest Icelandic eruption since 1783-1784 Laki eruption. The lava flow of about 84 km² area formed north of the Vatnajökull glacier at Holuhraun. Here, we explore the post-deposition evolution of this lava flow, both over time and space. We utilize synthetic aperture radar (SAR) acquisitions from the Sentinel-1 satellites of the European Space Agency on descending path 9, tracks 374-378 and ascending path 147, tracks 210-213. The Sentinel-1 satellite pair provides data ranging from the present back to the year 2014. Interferometric (InSAR) time series analysis of these data provides both a long term trend of deformation of the lava flow and its temporal and spatial evolution from two viewing angles. The different viewing geometries allow us to decompose the two line-of-sight observations into near-east and near-vertical deformation. The results show that dominant signals in the area are glacial isostatic adjustment (GIA), plate spreading and lava flow compaction due to cooling of the up to 40 m thick flow. After removal of GIA and plate spreading models, the remaining signal is predominantly lava flow compaction. We employ a first-order thermoelastic compaction model to infer the cooling history of the flow over the roughly 5-year observation period.