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

Abstract

Southeast Asia hosts a large number of active and well-studied volcanoes, the majority of which are located in Indonesia and the Philippines. Northern Southeast Asia (Myanmar, Cambodia, Laos, Thailand and Vietnam) also hosts volcanoes that for several reasons (post-World War II conflicts, poor accessibility due to dense vegetation, no known historical activity) have been little studied. Systematic assessments of the threat these volcanoes pose to resident populations do not exist, despite evidence of numerous eruptions through the late Pleistocene and likely even during the Holocene. A recent study that inferred the location of the Australasian meteorite impact (which produced the largest known tektite strewn field on Earth) beneath the Bolaven Volcanic Field in southern Laos provided a wealth of data for that volcanic field, in particular, mapping of vents and flows, and their absolute ages. Building upon this foundation, we used the Bolaven Volcanic Field as a case study for assessing the potential exposure of populations and infrastructure to lava flows during future eruptions there. Our study uses remote sensing of past flows, lava-flow simulations and open-access exposure data, to assess hazards and exposure. Our results show that future vents are most likely to occur in a N-S band atop the Bolaven Plateau, with some flows channelled into canyons that spill down the plateau flanks onto lower plains that support more populated areas such as the provincial centre, Pakse. Our exposure assessment suggests that around 300,000 people could experience socio-economic impacts from future eruptions. The largest impacts would be on two of the main economic sectors in the region, agriculture and hydropower. The potential also exists for life-threatening explosions from interactions between magma and surface waters, which are abundant in the region. We estimate an Average Recurrence Interval of approximately 10,400 years.