Volcanoes that dominate postcards and disaster movies are often the ones we can see, their peaks etched against the sky. Yet some of the most consequential volcanic threats on Earth are hidden under oceans, buried beneath cities, or so quiet that they barely register as hazards. The real risk, I would argue, lies in the systems we do not watch closely enough, even as they hold the power to disrupt global climate, aviation, and modern infrastructure.
From the seafloor off the Oregon Coast to sprawling calderas in densely populated regions, scientists are racing to understand how these obscured volcanoes behave and how much warning they might give. Their work suggests that the next globally disruptive eruption is more likely to come from a volcano that blends into the landscape or lies far below the waves than from a famous cone that tourists already fear.
The invisible majority of Earth’s volcanoes
Most people picture a volcano as a steep cone, but a large share of Earth’s active systems are either underwater or hidden beneath thick vegetation and ice. Submarine volcanoes in particular are almost entirely out of sight, yet they build new crust, reshape coastlines, and occasionally trigger tsunamis without ever breaking the ocean surface. Mapping projects around places like the Pacific have revealed extensive volcanic fields that only appear as subtle bumps on bathymetric charts, such as the seamounts cataloged near remote oceanic regions.
On land, the same invisibility problem plays out in different ways. Some calderas are so broad that entire towns and farmland sit inside them, with no obvious central peak to signal danger. Others are cloaked by forests or urban development, their vents scattered across hills that look ordinary until they erupt. In volcanic arcs that stretch from places like tectonic plate boundaries to continental interiors, the line between extinct and merely dormant is often blurry, which complicates how authorities prioritize monitoring and land use.
Why hidden systems can be more dangerous than iconic peaks
High profile volcanoes attract instruments, funding, and public attention, which means their unrest is more likely to be caught early. The quieter systems, by contrast, may have only a handful of seismometers or none at all, so their first clear signal can be a sudden eruption. That asymmetry is why some researchers argue that the greatest global risk comes from volcanoes that are poorly monitored, poorly understood, or both, including vast calderas that underlie regions like densely populated basins.
When such a system erupts at scale, the consequences can extend far beyond local ashfall. A large explosive event can inject sulfur-rich aerosols into the stratosphere, dimming sunlight and altering climate patterns for years. Recent analyses of so-called “hidden” volcanoes emphasize that these under-the-radar systems are the ones most likely to produce a global crisis, from disrupted food supplies to grounded aircraft, as ash and aerosols spread across continents and even close air space over regions such as northern India, according to work on the world’s largest calderas.
What current eruptions reveal about the Ring of Fire
One way to grasp the scale of volcanic activity is to look at a single year. According to the Global Volcanism Program, There were 63 confirmed eruptions at some point in 2025 Apr 30, a reminder that the planet’s crust is constantly shifting and venting. Many of these eruptions cluster along the Pacific Ring of Fire, where subducting plates feed chains of volcanoes that arc around the ocean basin.
Visualizations of where lava is currently flowing show how these eruptions are distributed from Alaska to Indonesia, with hotspots in regions like Kamchatka, Japan, and the Andes. Interactive maps that track volcano eruptions highlight how some systems erupt persistently with modest lava flows, while others remain quiet for centuries before unleashing a single, massive blast. That pattern underscores why long-dormant or little-known volcanoes deserve as much scrutiny as the famous peaks that erupt more often but with smaller, more manageable events.
Axial Seamount and the lesson from an “unusual” underwater volcano
Few volcanoes capture the paradox of invisibility and risk as clearly as Axial Seamount, an active underwater volcano off the Oregon Coast that scientists have been watching for decades. Located roughly 300 miles off the coast of Oregon, Axial Seamount sits along a mid-ocean ridge where new crust is constantly forming. Its eruptions in 2011 and 2015 were detected largely through seafloor instruments and changes in the shape of the volcano, not through dramatic images of ash plumes or lava fountains.
Earlier forecasts suggested that this “unusual” underwater volcano might erupt again by the End of 2025, based on patterns of inflation and Frequent earthquakes recorded by ocean observatories. Reports described how an unusual underwater volcano off Oregon was showing signs of renewed activity, while another analysis framed it as An Underwater Volcano Off of Oregon Coast May Erupt by End of the decade, emphasizing how closely scientists have worked with Axial Seamount for years to refine their models of its behavior through detailed monitoring.
When forecasts shift: from 2025 to mid-to-late 2026
As more data came in, Researchers adjusted their expectations for Axial Seamount, illustrating how dynamic and uncertain volcano forecasting can be. An earlier projection that the underwater volcano off the Oregon Coast would erupt in 2025 was based on the timing between previous events and the rate at which magma appeared to be refilling the system. Coverage of the underwater volcano off Oregon Coast noted that scientists were comparing current signals to those that preceded the 2011 and 2015 eruptions.
Later in the year, new analyses suggested that the volcano likely will not erupt until mid-to-late 2026, extending the forecast window and highlighting how even well-instrumented systems can surprise experts. One report on an active underwater volcano off Oregon Coast described how the updated models pointed to a slower buildup of pressure, while another account of an Underwater volcano off Oregon coast likely won’t erupt before mid-to-late 2026 explained that Researchers thought that Axial Seam would erupt sooner, only to find that the system was taking longer to blow its top based on revised seafloor measurements.
Campi Flegrei and the threat beneath a major city
Hidden volcanoes are not only a problem offshore. In southern Italy, Campi Flegrei is a sprawling volcanic system Located just east of Naples, with more than a million people living in and around its caldera. Unlike the iconic cone of Vesuvius, Campi Flegrei is a patchwork of craters, fumaroles, and uplifted ground that blends into the urban fabric, making it easy to forget that the entire area sits atop a restless magma system. The Effects of a major eruption here would be catastrophic for Naples and could send ash across much of Europe.
Analyses of Campi Flegrei often place it among a short list of volcanoes that could “shut down the world,” not because it is guaranteed to erupt soon, but because its potential impact is so large and its signals are complex. Ground deformation, gas emissions, and seismic swarms have all waxed and waned over recent decades, forcing authorities to weigh the costs of evacuation against the risk of a false alarm. For residents, the danger is literally beneath their feet, yet the lack of a towering peak can make the hazard feel abstract until the ground starts to shake.
Pinatubo and the surprise factor of “quiet” volcanoes
History shows that some of the most consequential eruptions have come from volcanoes that were not even recognized as active. A striking example is Pinatubo in the Philippines, which produced a colossal eruption in 91 that cooled global temperatures and injected vast amounts of sulfur into the stratosphere. Before that event, Pinatubo was not widely monitored or feared, and it was not even known to be an active volcano years before its major eruption, according to discussions among volcanologists and enthusiasts who have dissected the case in detail on forums like r/Volcanoes.
That eruption is now a textbook example of how a seemingly modest mountain can generate VEI 7 events, a scale of explosivity that rivals the largest eruptions of the past few centuries. For scientists, Pinatubo underscored the need to survey and classify volcanoes that have little historical record but sit in tectonically active regions. For policymakers, it highlighted the importance of flexible emergency plans that can be activated quickly even when a volcano has not been on the traditional watch list, because the next “quiet” system to awaken may give only weeks or months of clear warning.
Health, aviation, and the less obvious fallout of eruptions
When a volcano erupts, the immediate images tend to focus on lava and ash, but some of the most dangerous effects are less visible. Volcanic gases are particularly hazardous, especially sulfur dioxide, carbon dioxide, and fluorine-rich compounds that can pool in low-lying areas or travel long distances in the atmosphere. People can be exposed to harmful volcanic gases by breathing them in or through contact with the skin and eyes, and these emissions can also corrode infrastructure, contaminate water supplies, and pose a health hazard inside planes that inadvertently fly through contaminated airspace, according to detailed assessments of volcanic hazards.
Aviation is particularly vulnerable to eruptions that do not make global headlines. Fine ash can sandblast jet engines, clog sensors, and reduce visibility, which is why airlines reroute flights even for moderate eruptions that loft ash into common cruising altitudes. Analyses of current activity show how ash clouds from volcanoes along the Ring of Fire can intersect with busy transoceanic routes, forcing detours and delays. Graphics that invite readers to See where Volcanoes are erupting emphasize that even relatively small events can have outsized impacts on global travel when ash drifts into key corridors, which is why early warning systems for eruptions are now a priority for both scientists and aviation authorities.
Monitoring the unseen: from ocean cables to satellite eyes
Keeping track of hidden volcanoes requires a different toolkit than watching a smoking summit from a nearby observatory. On the seafloor, networks of pressure sensors, seismometers, and fiber-optic cables detect subtle changes in depth and vibration that signal magma movement. The long-term work around Axial Seamount, for example, has relied on ocean observatories that continuously measure how the volcano inflates and deflates, allowing scientists to refine their forecasts even when no one can see the eruption directly. Reports on an active underwater volcano off Oregon Coast describe how these instruments captured the pattern of inflation that preceded past eruptions and now inform updated timelines.
In the air and in orbit, satellites track thermal anomalies, gas plumes, and changes in ground elevation that can reveal unrest at remote or little-known volcanoes. Combined with global seismic networks, these tools help scientists flag unusual activity even in regions with sparse local monitoring. Interactive graphics that show how Natural disasters, from wildfires to eruptions, are distributed around the world rely on such satellite data to map where lava is flowing and where ash is spreading, as in recent visualizations that invite readers to See global activity. The challenge now is less about detecting that something is happening and more about interpreting what those signals mean for communities on the ground and for systems like aviation and power grids that can be disrupted far away.
Public awareness and the politics of invisible risk
Even the best monitoring is only as effective as the public’s willingness to act on warnings, and that is harder when the threat is not obvious in the landscape. Communities living near broad calderas or offshore volcanoes may not identify as being in a hazard zone, which can make evacuation orders or land-use restrictions politically contentious. In regions like the Oregon Coast, where tourism and fishing are economic pillars, messaging about an underwater volcano that might erupt in the coming years has to balance scientific caution with the reality that the most likely impacts are subtle seafloor changes rather than dramatic coastal destruction, as explained in coverage of what an eruption offshore would mean.
Globally, scientists who study hidden volcanoes argue that public communication needs to move beyond dramatic imagery of lava and ash toward a more nuanced understanding of cascading risks, from climate impacts to supply chain disruptions. Analyses of the world’s “hidden” volcanoes that pose the greatest risk for global crisis emphasize that the systems most likely to cause widespread disruption are not necessarily the ones that look most threatening on the surface, but those that intersect with dense populations, critical infrastructure, and key atmospheric corridors, as seen in assessments of global crisis scenarios. For policymakers, that means investing in monitoring and preparedness for volcanoes that the public may barely know exist, because the most dangerous eruptions of the future may come from places that are, for now, almost invisible.
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