Hazards from lava–river interactions during the 1783–1784 Laki fissure eruption

Abstract

Interactions between lava flows and surface water are not always considered in hazard assessments, despite abundant historical and geological evidence that they can create significant secondary hazards (e.g., floods and steam explosions). We combine contemporary accounts of the 1783−1784 Laki fissure eruption in southern Iceland with morphological analysis of the geological deposits to reconstruct the lava−water interactions and assess their impact on residents. We find that lava disrupted the local river systems, impounded water that flooded farms and impeded travel, and drove steam explosions that created at least 2979 rootless cones on the lava flow. Using aerial photographs and satellite-derived digital terrain models, we mapped and measured 12 of the 15 rootless cone groups on the Laki lava field. We have identified one new rootless cone group and provide data that suggest another cone group previously attributed to the 939−940 CE Eldgjá eruption was created by the Laki eruption. We then use contemporary accounts to estimate formation dates and environments for each cone group, which formed in wetland/lake areas, on riverbeds, and near areas of impounded water. Furthermore, comparison with previous field studies shows that assessments using remote sensing can be used to identify and map meter-scale and larger features on a lava flow, although remote mapping lacks the detail of field observations. Our findings highlight the different ways in which lava can interact with surface water, threatening people, property, water supplies, and infrastructure. For these reasons, anticipation of such interactions is important in lava flow hazard assessment in regions with abundant surface water; we further demonstrate that remote sensing can be an effective tool for identifying lava−water interactions in past lava flows.

Assessment of geological hazard susceptibility based on remote sensing images

“…They collected basic information such as topography and elevation at different places in the study area to simulate the possible formation of a weak layer on a hillside up to collapse [23]. In order to quantify the heights of ground objects such as vegetation and buildings, the most common method of analyzing elevation data is to generate Differential DEMs (DoDs) showing pixel-by-pixel differences between multi-temporal DEMs (e.g., to quantify vertical changes in erosion/deposition and buildings), or pixel-by-pixel differences between a digital surface model and a digital terrain model [16,27]. The accuracy of digital elevation models (DEMs) impacts the generation of geomorphic parameters, but high-resolution DEMs do not always ensure high slope and aspect accuracy [28].…”

Assessing Volcanic Hazard and Exposure at Obscure Volcanic Fields: A Case Study from the Bolaven Volcanic Field, Laos

“…there is no involvement of new magma, and the explosions can take place even kilometres away from the vent), forming rootless cones (e.g. Boreham et al, 2020;Fitch and Fagents, 2020). Secondary phreatomagmatic explosions are more likely if there is interaction between fresh low-viscous lava and water-saturated sediments in an unconfined environment (Zimanowski and Wohletz, 2000;Schipper et al, 2011).…”

“…The lava solidifies and creates new land, resulting in deflection (e.g. Pedersen et al, 2017) or blocks the river, with consequent upstream flooding (Boreham et al, 2020). Approximately 60% of the simulated inundation area of the BVF is covered by post-impact lava, with a good part of it turned into saprolite, and the remaining ~40% being Mesozoic (mudstone and sandstone) and Holocene fluvial/lacustrine sediments (loose coarse silt to fine sand).…”

Attempt to Model Lava Flow Faster Than Real Time: An Example of La Palma Using VolcFlow

“…Lahars and jökulhaups result from snow or ice melting [12][13][14][15]; toxic gas can come from lava degassing, lava interacting with a body of water, or from the fires started by lava [16]. Terrain collapses: earthquakes and landslides are also on the long list of processes an eruption may trigger [17][18][19][20]. Unlike other natural phenomena, volcanic eruptions may not be continuous; hence, they are frequently described in episodes with various processes and products within an indeterminate time frame of variable magnitude or intensity.…”