Volcanic eruptions in a multi-hazard world: a global assessment of past volcanic multi-hazard events

Volcanic eruptions rarely occur as isolated hazards. Instead, they produce interacting or cascading processes and, at times, interact with other non-volcanic hazards. Volcanic activity can produce hazards such as tephra fall, lava flows, or pyroclastic flows, which may trigger secondary hazards including fires, floods, and lahars. In a changing climate, eruptions may also intersect more frequently with external events such as tropical storms or wildfires, amplifying their impacts and complicating risk management. Past examples, such as the 1991 Pinatubo eruption during Typhoon Yunya, or the lava flows and tephra from the 2021 Tajogaite eruption on La Palma, show how compounding hazards can extend the impacts of eruptions far beyond the volcanic slopes and intensify damage to the built environment and agriculture. Despite these observations, the global patterns of such occurrences remain largely unquantified, and volcanic hazards are still often considered in isolation, leaving a gap in understanding the wider multi-hazard context in which eruptions occur.

In order to fill this gap and understand where volcanic multi-hazards may happen in the future, a first step is to look back at the past to identify where volcanic hazards have coincided with other hazards. In this project, we interrogate past event datasets, including the Global Volcanism Program eruption list and the MYRIAD-HESA multi-hazard event dataset, to identify global locations where hazards coincided in the past. We define a volcanic multi-hazard event as an eruption during which at least one additional volcanic or non-volcanic hazard occurs within a size-dependent radial buffer around the volcano and within the eruption time window. Events are classified by volcano type, VEI (Volcanic Explosivity Index), and length of eruption.

Hazard interactions were grouped into geophysical events, meteorological events, and climatological extremes, and preliminary results reveal that tsunamis, tropical cyclones, and heatwaves dominate interacting hazards within these categories. Multi-hazard events are most often associated with stratovolcanoes when analysed at the eruption level. To explore implications for risk and exposure, we identify areas of increasing population using GHS-POP global datasets, highlighting Southeast Asia as a key exposure hotspot of rapidly growing urban populations. This approach provides new insights into volcanic multi-hazard environments and represents a first step towards identifying where future multi-hazard events may intersect with growing exposure, informing integrated multi-hazard risk assessment.