Mapping of lava flows based on remote sensing data of high accuracy has become a common tool for exploring volcanic eruptions in greater detail. Mapping data based on remote sensing data provides information on the location and flow direction of lava flows as well as their areas and enables the localisation of volcanic vents-valuable knowledge for pre-and post-eruption volcanic activity and behaviour estimations. The current research seeks to expand the understanding of the volcanic and tectonic processes in Harrat Lunayyir, Saudi Arabia. In view of this, remote sensing data was classified using iterative self-organising data analysis technique (ISODATA) algorithms. The aim of the classification is to identify spectral top-of-atmosphere (TOA) reflectance values to distinguish layers of old and recent lava flows based on differences. As a result, three distinct basaltic units were identified to have the following ages: 15.1 ± 6.1 ka (4%), 15.0 ± 8.4 ka (6%), and 14.6 ± 23.1 ka (10%). The differences in the calculated areas of the lava flows as mapped based on the remote sensing data and earlier modelling are captured and identified in relation to the local geomorphologic and geologic structures. The differences can be partly explained as being related to a considerable weathering of the observed geological formations at 800-1600 nm, with reflectance of 12%. The limitation of the methodology relates to the lack of accurate geochronological timeline, that is, an inability to identify accurate age of the samples.
The 2009 seismic episode at Harrat Lunayyir signalled a renewed geohazard and resulted in a regional dyke that propagated to a very shallow depth (a few hundred metres) below the surface. Since then, there has been an extensive research debate over the potential links between the volcanic/intrusive activity and tectonic processes, particularly because the earthquake swarm and dyke propagation did not eventually result in an eruption. The current study seeks to estimate the relative changes in surface temperatures as a means for detecting an impending dyke-fed eruption or, alternatively, dyke arrest at a shallow depth. An analysis of thermal (infrared) data with a focus on the spatial distribution of land surface temperatures over a longer period of observation may help reveal the link between volcanic activity and dyke propagation. Here, the land surface temperature changes in the centre of Harrat Lunayyir were recorded when the 2009 dyke was propagating toward the surface. The spatial distribution of the land surface temperatures in the area indicated the segmentation of the dyke and suggested the segments were arrested at somewhat different depths below the surface.
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