Spatial and temporal controls on pyroclastic flow hazard at Arenal volcano, Costa Rica

Pyroclastic flows represent the greatest volcanic hazard at Arenal volcano, Costa Rica, due to their recurrence, unpredictability, potential run outs, high velocities and short emplacement times. The main pyroclastic flow events occurring at Arenal during the present period of eruptive activity have been characterized and simulated using the geophysical flow model TITAN2D. The simulations performed, coupled with analyses of the evolution of Arenal concerning the topographic and morphological development of the volcanic edifice and the eruptive activity; provide insight into various temporal and spatial patterns of pyroclastic flow hazard. Increased pyroclastic flow frequency is shown to be related to the vertical growth rate of the active crater. The topographic evolution of the volcanic edifice and of the morphology of the lava field explain several observed spatial hazard patterns relating to flow directionality and run-out, and lava effusion rates are shown to be related to pyroclastic flow magnitude and volume. Identified patterns highlight the dynamism of pyroclastic flow hazard at Arenal, and its close relationship to the evolution of the volcanic edifice and of the eruptive activity. The simulations performed also draw attention to the sensitivity of pyroclastic flow emplacement to topographic features and to topographic change, highlighting the importance of up to date and accurate representations of the topography (DEMs) of the volcano for related hazard assessments.

► Identification and analyses of determinants of pyroclastic flow hazard at Arenal volcano. ► The topographic evolution of the volcanic edifice is closely related to pyroclastic flow generation. ► Declining magma effusion rates are related to the production of smaller pyroclastic flows. ► TITAN2D simulations and other analyses show topographic controls of pyroclastic flow hazard. ► Identified spatial pyroclastic flow hazard patterns at Arenal are dynamic; i.e. they evolve in time.