The massive eruption of the Hunga Tonga–Hunga Ha‘apai volcano this January in Tonga, in the south Pacific Ocean, was the volcanic equivalent of a ‘near miss’ asteroid whizzing by the Earth. The eruption was the largest since Mount Pinatubo in the Philippines blew in 1991, and the biggest explosion ever recorded by instruments.

Ash fell over hundreds of kilometres, affecting infrastructure, agriculture and fish stocks. The damage caused amounted to 18.5% of Tonga’s gross domestic product. Submarine cables were severed, cutting off Tonga’s communications with the outside world for several days; farther afield, the blast created a worldwide shockwave and tsunamis that reached Japanese and North and South American coastlines. Mercifully, the eruption lasted only about 11 hours. Had it gone on for longer, released more ash and gas or occurred in more densely populated areas of southeast Asia, or near a high concentration of vital shipping lanes, electricity grids or other crucial global infrastructure, it would have had repercussions for supply chains, climate and food resources worldwide1.

And yet, little investment has gone into limiting what an eruption of this magnitude could do. Impacts would cascade across transport, food, water, trade, energy, finance, and communication in our globally connected world.

Deep impact

Although researchers have long known of the drastic impacts of large-scale volcanic eruptions, the likelihood of such an event has only recently been clarified.

The recurrence rate of large eruptions can be determined by searching the long-term records for sulfate spikes, stemming from the gas released during globally significant events. In 2021, researchers looked at ice cores from both poles and identified 1,113 signatures of eruptions in the Greenland ice and 737 in Antarctica, occurring between 60,000 and 9,000 years ago. They found 97 events that probably had a climatic 

Pinpoint the risks

Of the 97 large-magnitude volcanic eruptions detected in ice-core records, only a handful could be attributed to specific volcanoes. The sites of others remain a mystery, including some that occurred startlingly recently — for example, the eruptions that led to the ‘Late Antique Little Ice Age’ in the mid-sixth century. Estimates show that up to 80% of magnitude-6 eruptions before ad 1 are currently missing from the global geological record9, with especially poor data for oceanic islands such as the Kuriles, as well as Indonesia and the Philippines, countries with some of the highest densities of volcanoes.

Some 1,300 volcanoes have erupted at some point during the past 10,000 years, meaning they are considered active. But there are probably many other active volcanoes: their recent eruptions might not be known because their locations haven’t been studied, or they may have lain dormant for a long time but still be capable of a large explosive event. Identifying potentially active volcanoes10 requires a comprehensive approach. 7 eruption or greater.

Ramp up preparedness

To increase resilience at the community level and to support the humanitarian responses, real-time monitoring and simulations of ash fallout, gas plumes and other hazards, such as volcanic flows, should be fed into real-time, targeted communication. This ‘nowcasting’ advice could be delivered by SMS, instructing someone to ‘clear Volcanic ash off your roof to prevent collapse, as 50 centimetres of ash is expected over the next 2 hours’, for example, or directing them to the nearest centres for emergency supplies and health-care.

Improve monitoring

Only 27% or so of the Eruptions since 1950 have been monitored with at least one instrument such as a seismometer11. Data from only about one-third of these eruptions have been collected by the global database for volcanic unrest, WOVOdat. Improved ground-based monitoring of known active volcanoes — including measures of seismicity, gas release and ground deformation — could provide better advance warning of eruptions, especially when combined with emerging analyses that are aided by artificial intelligence.

Where local ground-based monitoring is not feasible, particularly in remote areas, satellite and aerial observation become essential. In addition to monitoring thermal, gas and deformation changes, satellites could provide real-time mass eruption rates, plume heights and imagery for disaster relief. But current satellites lack the necessary resolution in time and space