Biogeomorphological Evolution of Arenal Stratovolcano: A Field Laboratory to Investigate Relationships Between Volcanic Activity, Erosion, and Vegetation Succession

Arenal is a small Holocene twin stratovolcanoVolcano (~33 km2, ~ 9 km3, 1684 m a.s.l., ≥ 7 ka), almost symmetrical but with some slope irregularities because it is composed of overlapping lava fields (lava armour) in the central area, with a medium to distal zone comprised of tephra, and hyperconcentrated flow deposits on its flanks (tephra and epi-volcaniclastic apron). We present an up-to-day summary of the prehistorical and historical processes, based on morphometric, morphogenesis, and morphochronological information, the last one obtained by radiocarbon dating and historical records. The eruptive foci during the last 3 ka reflect local structural controls that produced different lava fields, with different grades of vegetation and soil development. The difference in age between the zones of the lava fields has an important role in the successional stage of the vegetation community and, therefore, on the erosionErosion rate. Lower the average erosionErosion rate and smaller range of variation over the years are recorded on older flows. The historical lava fields (1968–2010) have shown that the average erosionErosion rate on the complete lava field has decreased from 50.77 t ha−1 y−1 to 40.99 t ha−1 y−1 in 2010–2020. The results confirm that plant recolonization plays an important role in erosionErosion control at Arenal volcanoVolcano. At present, the areas of greatest vulnerability to erosionErosion processes are in the gullies and rockfall channels in the upper lava field but they will stabilize in the near future.