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Attracted by the breathtaking landscapes and fertile land, humans have established cities near volcanoes for millennia. However, when these volcanoes suddenly erupt, it often spells disaster. The specific dangers vary depending on the volcano, but typically include earthquakes, toxic gases, ash fallout, lava streams, scorching pyroclastic clouds, mudflows, and landslides.
While we now have a greater understanding of the risks posed by famous volcanoes like Vesuvius, Mount Rainier, and Pinatubo in the Philippines, these aren’t the only ones posing a threat to cities. Scientists and urban planners are also concerned about several lesser-known volcanoes, which may be just as hazardous.
10. Harrat Rahat, Saudi Arabia
Medina, one of the holiest cities in Islam and second only to Mecca, sees a surge of over two million pilgrims during Ramadan, significantly increasing its population. This poses a challenge, as Saudi Arabia's largest lava field, Harrat Rahat, is located just outside the city's expanding boundaries.
Many people are unaware that Saudi Arabia has active volcanoes, which rarely concern local urban planners due to their location in remote or uninhabited regions. However, in AD 1256, a lava flow from Harrat Rahat came as close as 4 kilometers (2.5 miles) to Medina. A similar eruption today could potentially bring lava into the expanded city. Even if lava doesn’t reach the city, it could disrupt transportation and cut off essential supplies like food, water, and medical aid, as ash would prevent air deliveries. With millions of people in panic, this could escalate into a major natural catastrophe.
9. The Tatun Group
Taipei, the bustling capital of Taiwan, is home to over 2.5 million residents. While it serves as a global hub for business, the local Tatun Group isn’t a company—it’s a cluster of approximately 20 volcanoes, one of which lies just 15 kilometers (9 miles) north of the city.
The Tatun Group was highly active during the Holocene period, with eruptions ceasing around 13,000 years ago. However, the most recent eruption occurred about 6,000 years ago, a brief period in geological terms. This eruption was a phreatic event—an explosion of steam, likely with some lava release. A similar phreatic eruption tragically claimed 57 lives at Japan’s Mount Ontake in 2014. Around 200 survivors managed to find shelter from the volcanic ash and gases.
Phreatic eruptions are extremely difficult to forecast, as they typically don’t involve deep seismic activity that can be monitored. Instead, these eruptions happen when existing magma deposits interact with groundwater, turning it into superheated steam that causes an explosive release, shattering surrounding rocks. A similar event today could bring havoc to the high-tech city of Taipei, which is why Taiwan’s National Science Council has set up an observatory to keep a vigilant eye on the Tatun Group.
8. Chichinautzin
Mexico City, home to nine million people, is surrounded by towering, picturesque volcanoes. However, the Chichinautzin volcanic field, much less scenic and located within the city itself, poses the most immediate volcanic threat. The last eruption in this area took place around AD 400 and was significant, with a Volcanic Explosivity Index (VEI) rating of 3. This eruption is believed to have caused a major humanitarian crisis, destroying ancient settlements, including the earliest known urban center in the Central Mexican highlands.
Chichinautzin is a monogenetic volcanic field, meaning each volcano erupts only once before becoming extinct, with future eruptions occurring at different locations. The infamous Paricutin eruption, where a massive volcano unexpectedly rose from a rural cornfield in Mexico, is considered to be similar to the AD 400 eruption from the Xitle cone in Chichinautzin.
Today, the southern part of Mexico City and the National University of Mexico sit atop the lava flow from Xitle’s eruption. While that specific cone is unlikely to erupt again, there’s potential for a new volcano to emerge anywhere within the Chichinautzin field. To make matters worse, Mexico City currently lacks a comprehensive volcanic hazard assessment.
7. Mount Baker
Mount Baker, the tallest mountain in the Northern Cascades, is a volcano located in Washington State, near the Canadian border. Though it may seem distant, any significant eruption from Mount Baker could have far-reaching consequences. Like its more famous counterpart, Mount Rainier, Baker is a stunning, glacier-covered peak, but it has a disturbing tendency to erupt and collapse, triggering massive mudflows known as lahars. The last such event occurred about 6,500 years ago, and Mount Baker remains an active volcano.
Another major collapse could have disastrous effects on the nearby small towns. Additionally, emergency planners in Canada are concerned that the resulting mudflows from such an eruption could redirect Washington’s Nooksack River into British Columbia, potentially causing widespread flooding. This flood could flow down the Fraser River, affecting Vancouver, the largest city in the province.
The most recent confirmed eruption of Mount Baker occurred in 1880, but its Sherman Crater has been exhibiting signs of volcanic activity since 1975. While monitoring efforts were ramped up at the time, they have since declined, and the US Geological Survey now deems the current monitoring efforts insufficient. This is especially concerning because flank collapses often happen suddenly and without much forewarning. When such an event occurs, the only option is to try to escape the danger.
6. Nyiragongo
Nyiragongo is an enormous volcano located in the Democratic Republic of the Congo, home to the world’s largest lava lake. This lava is exceptionally fluid, so whenever the lake drains, it rushes down the steep slopes of the volcano, devouring anything in its path. Unfortunately, the city of Goma, with a population exceeding one million, lies at the foot of the volcano. Additionally, Lake Kivu, situated nearby, has been gradually accumulating dissolved gases from Nyiragongo for millennia.
When the lava lake overflowed in 2002, molten rock surged through Goma, claiming the lives of 147 people, destroying 13 percent of the city, and forcing hundreds of thousands of residents to flee. Meanwhile, the gases seeping into Lake Kivu have raised concerns about the potential for a limnic eruption—a deadly explosion of carbon dioxide. The most infamous example occurred in 1986 when Cameroon’s Lake Nyos erupted, killing nearly 2,000 people instantly.
Nyiragongo isn’t the only active volcano in the region—nearby Nyamulagira erupted in 2010. Luckily, the lava from Nyamulagira flowed away from Goma and into Virunga National Park, causing minimal damage. Nevertheless, it’s no surprise that Goma has earned the title of the 'most dangerous city in the world.' While Nyiragongo and Nyamulagira continue to be active, political instability in the area has made it difficult for scientists to establish an observatory to monitor them.
5. The Auckland Volcanic Field
Auckland, New Zealand’s largest city, is located in the middle of a monogenetic volcanic field where over 50 volcanoes have erupted once and become extinct. This activity is fueled by a hot spot about 100 kilometers (62 miles) beneath Queen Street. The most recent eruption occurred around AD 1350, creating Rangitoto Island, the largest volcano in the field.
Although the possibility of another eruption in Auckland sounds concerning, it is likely that the impact will be limited to a portion of the city. The problem is that no one knows exactly where it will occur. The odds of an eruption happening in any given year are 1 in 1,000. As a result, geologists are keeping a close watch on the area, using seismometers placed in underground boreholes to avoid interference from the city’s own seismic 'noise.' Currently, everything is reported to be calm.
4. The Marsili Seamount
Marsili is Europe's largest active volcano (though it’s not the only European volcano on this list), appearing as an underwater ridge that stretches for more than 50 kilometers (30 miles). Scientists believe it has been active for thousands of years, with eruptions occurring around 3000 and 1000 BC. Presently, it continues to rumble and emit heat.
Marsili remains relatively unknown because it was only discovered in the early 2000s. Despite being entirely submerged, its location off the western coast of Italy places it in close proximity to numerous densely populated cities and towns. This is concerning, as scientists now suspect Marsili is unstable and could erupt at any moment.
Similar to Mount Baker in the Pacific Northwest, Marsili has the potential for explosive eruptions that could cause its walls to collapse, leading to a sudden tsunami. Approximately 17 percent of all volcanic-related fatalities are caused by such tsunamis. Between the eruption and the resulting tsunami, millions could be at risk of death across southern Italy.
3. Japan’s Volcanoes
Japan is a technologically advanced nation with a dense population and numerous volcanoes. While Mount Fuji is the most famous, Japan is home to even larger volcanoes, and there is a small possibility that one of them (though it’s uncertain which one) could erupt in the near future.
In 2014, two volcanologists from Kobe University in Japan studied the potential consequences if one of Japan’s caldera volcanoes, like Aira, which has been extensively studied, were to experience a supereruption. Their findings were grim. Essentially, the entire country could be buried under several feet of ash, and the human toll would be even more catastrophic.
Japan must seriously consider the worst-case scenario. Over the next century, the two scientists estimated there is a 0.73–1.0 percent chance of a Magnitude 7 eruption and a 0.25–0.26 percent chance of a Magnitude 8 eruption. While these probabilities appear low, it’s important to note that just before the 1995 Kobe Earthquake, the 30-year probability for such an event was 0.38–7.8 percent.
It’s incredible how such dry, technical language can carry such a chilling impact.
2. Campi Flegrei
While we are all familiar with the devastation Mount Vesuvius caused in Pompeii in AD 79, many people are unaware of an even larger threat looming over the city of Naples, Italy. This volcano, Campi Flegrei (sometimes referred to as the Phlegrean Fields), far surpasses Vesuvius in size. The volcanic fields cover nearly everything in the NASA image above, including the bay. It’s so immense, you need to view it from space to grasp its scale.
Why, then, would anyone choose to build part of Naples inside a supervolcano? The answer lies in the fact that for centuries, no one even realized it was there. Unlike Vesuvius, Campi Flegrei is relatively flat due to the collapse following a colossal eruption 40,000 years ago that emptied its enormous magma chamber (which is connected to the chamber beneath Vesuvius). The eruption’s effects were felt across the northeastern Mediterranean, spanning from Italy to western Turkey and Russia.
Campi Flegrei remains active today, and while it’s being closely monitored, emergency responders face a massive challenge. Approximately 500,000 people reside inside the caldera, with another 2.5 million people living throughout the rest of Naples. While evacuation plans have been devised, the worst-case scenarios for Campi Flegrei are deeply unsettling.
1. The Laacher See
It may sound unbelievable, but Central Europe and the nations around the North Sea face a significant threat in the form of an active volcanic caldera filled with water, located less than 30 kilometers (20 miles) south of Bonn, Germany. While it’s important to note that it’s not quite the catastrophic event some online sensationalists claim, the Laacher See did unleash a massive eruption about 13,000 years ago.
The Laacher See is located in the eastern Volcanic Eifel mountain range, to the west of the Rhine and north of the Mosel. It is encircled by approximately 100 volcanoes, with another 240 in the western part of the range. Up until the 1970s, all of these volcanoes were believed to be dormant. However, parts of the Volcanic Eifel are rising by as much as 2 millimeters (0.07 inches) per year, and new signs of activity in the Laacher See have recently been discovered by scientists.
There is no hazard map for the Laacher See, but it has evidently had a profound effect on human societies in the past. When the volcano last erupted during the Stone Age, archaeologists believe it devastated the surrounding cultures, leading to the fragmentation of groups and the simplification of their toolkits. Although the Laacher See isn’t expected to erupt anytime soon, it’s crucial that authorities start preparing for the day it might.
