Within the volcanic risk literature, the typical focus of attention for global-scale catastrophes has been on large-scale eruptions with a volcanic explosivity index (VEI) of 7–81,2, which remain relatively rare3. The relationship between volcanic eruptions of this scale and global catastrophic risks (GCRs) – events that might inflict damage to human welfare on a global-scale4 provided rationality for this tendency. We define this correlation as a ‘VEI-GCR symmetry’, whereby as the magnitude of an eruption increases so too does the probability of a GCR event. The eruption of Tambora in 1815 (VEI 7) is an example of the mechanism that governs the VEI-GCR symmetry, in which a large release of sulfur into the stratosphere brought about periodic global cooling, widespread frosts in the northern hemisphere, and crop failures across Europe5,6. This VEI-GCR symmetry has historically defined society’s relationship with volcanoes. Indeed, we have often failed to consider lower-magnitude VEI eruptions as constituting GCRs.

Here, we argue that this symmetry has become imbalanced towards ‘VEI-GCR asymmetry’, driven by clustering of our global critical systems and infrastructures in proximity to active volcanic regions. Critical systems and infrastructures, such as shipping passages, submarine cables, and aerial transportation routes, are essential to sustain our societies and to ensure their continued development7,8. We observe that many of these critical infrastructures and networks converge in regions where they could be exposed to moderate-scale volcanic eruptions (VEI 3–6). These regions of intersection, or pinch points, present localities where we have prioritised efficiency over resilience, and manufactured a new GCR landscape, presenting a new scenario for global risk propagation.

A manufactured global catastrophic risk landscape

Chinese–Korean pinch point

The Changbaishan volcanic complex encompassing Mount Paektu straddles the Chinese-North-Korean border, and is most known for its 946 C.E. ‘millennium eruption’ which was estimated to be a VEI 7 eruption. Tephra deposits from this eruption have been documented as far as Hokkaido, Japan14, demonstrating the capability of this volcano to cause widespread disruption in the region. An eruption column, even from a smaller-scale eruption (VEI 4–6) at Mount Paektu could be capable of producing a tephra column that would disrupt some of the busiest air routes in the world, such as Seoul to Osaka and Seoul to Tokyo15 and to maritime traffic traversing the Sea of Japan.

Luzon pinch point

The Luzon Strait is a key shipping passage connecting the South China Sea to the Philippine Sea, and a key route for submarine cables, with at least 17 cables connecting China, Hong Kong, Taiwan, Japan, and South Korea. The Luzon Volcanic Arc (LVA) encompassing Mount Mayon, Mount Pinatubo, Babuyan Claro, and Taal volcanoes, among others, presents a possible location for an explosive eruption to disrupt the Strait. Volcanic ash and volcanically-induced submarine landslides and tsunamis in this region (particularly from submarine volcanic centres) would pose a risk to submarine cable infrastructure within the Strait, and result in the closure of the shipping passage. The 2006 7.0 Mw Hengchun earthquake off the south-west coast of Taiwan triggered submarine landslides that severed 9 submarine cables in the Strait of Luzon which connects Hong Kong, China, Taiwan, the Philippines, and Japan, resulting in near-total internet outages and severely disabling communication capacities (up to 80% in Hong Kong), with knock-on widespread disruptions to global financial markets. These disruptions continued for weeks in the aftermath, with repairs to the cables taking 11 ships 49 days to restore16.

North Atlantic pinch point

The aerial traffic between London and New York comprises over 3 million seats per year15. Disruption to this critical artery could cause widespread disruption and delay to global trade and transportation networks. Volcanic centres in Iceland are a potential source for this disruption, with numerous volcanic centres producing explosive events of VEI 3–6, including Katla (1918), Hekla (1947), and Grímsvötn (2011).

Pacific Northwest pinch point

An eruption of a Cascades volcano, such as Mount Rainier, Glacier Peak, or Mount Baker in Washington, would have the potential to trigger mass flows, such as debris avalanches or lahars, resulting from the melting of glaciers and ice caps, with the potential to reach Seattle20. The Osceola mudflow generated around 5600 years ago at Mount Rainier travelled over 60 miles to reach Puget Sound at the site of the present-day Port of Tacoma, Seattle. The generation of a similar-scale mass flow, and combined with any ash fall towards Seattle, would force provisional closure of airports and seaports, which account for 2.5% of the US’s total traffic respectively18. Volcanic ash might also affect wider airspace including parts of Canada, including Vancouver, and US cities such as Portland. Scenario modelling for a VEI 6 eruption at Mount Rainier with volcanic ash closing airspace across the northern USA and parts of Canada predict potential losses of up to US\$7.63 trillion dollars of global GDP output loss over a 5-year period18.

Reconsidering volcanic risk assessments

By converging critical systems within pinch point localities and placing them at the interface with regions of potential volcanic activity, we have manufactured a new type of GCR from lower VEI 3 to 6 magnitude eruptions; a narrative that has previously been neglected by the volcanic risk community. The identification of ‘pinch points’ tilts the relationship between volcanic activity and GCRs, towards VEI-GCR asymmetry, thereby presenting a current gap in our approach to volcanic risk assessment, and disaster prevention and mitigation practices. We suggest that the community should now consider this risk asymmetry in assessments, and work to fully understand the systemic vulnerabilities that may catapult us from a lower magnitude volcanic eruption (VEI 3 to 6) to a GCR.

As preparedness measures in the pre-disaster phase, we propose that systems mapping and evidence-based foresight activities, such as horizon scanning and event tree analysis be more systematically incorporated into work to identify the full extent and nature of our VEI-GCR asymmetry, and identify opportunities where resilience can be built towards global catastrophic volcanic risk. These activities ought to rely on expert elicitation, including from natural and geophysical sciences, civil engineering, and economics. The asymmetry mechanism discussed here in the context of volcanic hazards is also likely applicable to other geophysical phenomena; a similar approach could be considered for seismic, hydrogeological, and meteorological hazards alike, where this is not already the case.

Unlike super-volcanic eruption scenarios where we have little opportunity for prevention, we can work to reduce the fragility and exposure of our critical systems to rapid-onset natural events, and ultimately increase our resilience to GCRs.