Topographical constraints on fractal dimension of transitional lava flow morphologies: Insights from the 2022 Meradalir flow field, Iceland

Abstract Fractal analysis of lava flow margins can distinguish between pahoehoe and a’a’ end-member lava flow morphologies. However, the fractal dimensions of transitional lava flow morphologies have yet to be determined. This study investigates the fractal behavior of transitional lava flow morphologies emplaced during the 2022 Meradalir (Iceland) eruption. Orthomosaics and digital elevation models from seven days of the eruption were acquired, and the margins of the lava flows were traced and divided into segments based on morphology. Fractal analysis was carried out on the whole flow field and on the individual segments, and the obtained values were compared using statistical analysis. The results show that the fractal dimension of the flow field varies throughout the eruption, which may be caused by changes in the underlying topography. The fractal dimensions of slabby and spiny pahoehoe are similar, while rubbly pahoehoe yields lower values. This suggests a possible link between fractal dimension and degree of crust disruption. However, the results do not support defining expected ranges of fractal dimensions for these transitional morphologies. Fractal dimensions are low across the whole dataset (~ 1.020–1.100) which may be caused by underlying topography. The steep valley walls of Meradalir valley may inhibit lava flow branching, causing lower-than-expected fractal dimensions. Topography may thus limit the utility of fractal analysis to identify lava flow morphologies using remote sensing.