This post was authored by Dr Elinor Meredith, a former Research Fellow at the Earth Observatory of Singapore, and Natalie Teng. It was edited by Lauriane Chardot.
Around half of the world’s population living near volcanoes lives in cities. Cities near volcanoes concentrate dense populations, infrastructure, and buildings, making eruptions especially dangerous. An eruption can trigger effects that ripple far beyond the direct affected area, disrupting transport, utilities, and economies across the country. This leads to the question: which cities are most exposed to volcanic hazards?
In the past, many cities have been devastated by volcanic eruptions. In 79 AD, pyroclastic flows, which are fast avalanches of hot ash, gas, and material, were generated from Vesuvius in Italy and completely buried Pompeii. More recently, lava flows from Nyiragongo in the Democratic Republic of Congo have repeatedly swept through parts of Goma, with the last in 2021. Ashfall and subsequent mudflows from the 1991 eruption of Mount Pinatubo in the Philippines affected Angeles City and surrounding areas, while ashfall reached as far as Metro Manila, about 90 kilometres away. The 2010 eruption of Merapi in Indonesia sent deadly pyroclastic flows and mudflows into the outskirts of Yogyakarta, forcing hundreds of thousands of people to evacuate.
Eruption of Mount Pinatubo, June 15, 1991 (Source: NOAA/NGDC)
In a study recently published in Natural Hazards and Earth System Sciences, together with our co-authors, we ranked cities near active volcanoes by the number of people exposed, distance to the nearest volcano, and the number of nearest volcanoes nearby.
Across these three ranking criteria, the most exposed city is Bandung in Indonesia, with almost 9 million people exposed within 30 kilometres of up to 12 volcanoes, including Tangkuban Parahu, Guntur, and Papandayan volcanoes.
Stacked bar charts of city population exposure for the top 20 cities coloured by the number of volcanoes the populations are exposed to within 100 km of volcanoes (Source: Figure 5 of the publication).
Southeast Asia is the most exposed region globally with around 161 million people in cities living within 100 kilometres of a volcano. Indonesia stands out as the country with the highest number of cities and residents near volcanoes. Jakarta alone has more people living near volcanoes than entire populations of other countries, with around 38 million living within 100 kilometres of a volcano. Jakarta lies exposed to nine volcanoes, including Gede-Pangrango, Salak, and Perbakti-Gagak.
Elsewhere, the entire country of El Salvador lies within 30 kilometres of a volcano. Nestled between San Salvador and Ilpoango volcanoes, the capital city San Salvador is exposed to as many as 24 volcanoes.
Zooming in ever closer to the volcanoes, some cities such as Naples in Italy, Quito in Ecuador, and Managua in Nicaragua have large proportions of their population within 10 kilometres of volcanoes. In fact, some cities are located on top of volcanoes, such as Auckland on the Auckland Volcanic Field in New Zealand, Mexico City on the Chichinautzin Volcanic Field in Mexico, and Naples on the Campi Flegrei caldera in Italy.
Horizontal stacked bar charts of the city populations ranked by the number of people living within 100, 30, and 10 km from volcanoes and coloured by the distance to the nearest volcano. Each bar represents a city exposed to volcanoes (Source: Figure 4 of the publication).
In total, the study identified 1,133 cities, home to around 431 million people, located within 100 kilometres of 1,264 active volcanoes around the world. In a publicly available interactive web app that we developed as part of this study, one can select a city and see its exposure to nearby volcanoes. These rankings can be used to identify key hotspots of cities that need further localised investigation.
That kind of information will be essential for understanding how volcanic eruptions might impact specific cities and support urban planners, local authorities, and scientists to prepare for eruptions.
This research was supported by the Singapore Ministry of Education (MOE) under the Tier 3b project ‘Integrating Volcano and Earthquake Science and Technology (InVEST)’ (award number MOE-MOET32021-0002).