10 Most Likely Volcanoes to Erupt – and Their Global Consequences

In the last few years, volcanoes have kept turning up in the news cycle. Lava fountains on Iceland’s Reykjanes Peninsula have forced repeated evacuations. Steam-driven blasts at Taal in the Philippines have sent dark plumes into the sky. Ash from Colombia’s Nevado del Ruiz has risen high enough to trigger aviation alerts.

None of these events has been globally catastrophic. Yet they are reminders that Earth’s crust is restless. At any given time, around 40–50 volcanoes are in a state of continuing eruption, and more than 60 eruptions have been confirmed in 2025 alone. Most are small and far from major cities. A few sit close to millions of people, key trade routes, and critical infrastructure.

This article looks at 10 volcanoes that scientists watch especially closely – not because a major eruption is guaranteed soon, but because their mix of unrest, eruption history, and exposure means a future event could have serious regional or even global effects.

It explains how volcanologists judge which systems are “likely” to erupt, unpacks the current status of each of these high-profile volcanoes, and explores the global consequences that a major eruption could have for climate, aviation, food prices, and everyday life.

Key Points

• Dozens of volcanoes erupt each year, but a small group combines active unrest with dense nearby populations or critical infrastructure.

• Campi Flegrei in Italy, Ioto in Japan, and Iceland’s Reykjanes Peninsula are among the most closely watched systems today.Nature+2Live Science+2

• In the Americas, Nevado del Ruiz, Popocatépetl, and Mount Rainier pose high risk because of lahars, ash, and proximity to major cities.Global Volcanism Program+2Topo Streets+2

• In the Asia-Pacific, Merapi, Taal, Sakurajima, and Ioto are persistently active and capable of dangerous explosive eruptions.volcanodiscovery.com+2volcanodiscovery.com+2

• Yellowstone is unlikely to produce a super-eruption any time soon, but even modest activity would have wide media and market impact.Mount Nyiragongo+1

• Global consequences include disrupted air travel, short-term climate cooling from high ash injections, supply-chain shocks, and humanitarian crises.Wikipedia

Background

Volcanoes are not rare events. They are part of how the planet loses heat and recycles crust. The majority of eruptions are small to moderate and happen on isolated islands, mountain chains, or polar icecaps. They barely register outside specialist reports.

Risk rises when three elements overlap: an active or restless magma system, a history of dangerous eruptions, and people or infrastructure in harm’s way. A remote Alaskan volcano can erupt violently with limited direct impact. A smaller event near a major city can be far more disruptive.

The last few decades have delivered several “wake-up calls.” The 2010 eruption of Eyjafjallajökull in Iceland shut down European airspace for days, costing the aviation industry billions of dollars. The 2022 eruption of Hunga Tonga–Hunga Haʻapai blasted ash and water vapor to record altitudes and triggered a Pacific-wide tsunami, reminding scientists how powerful even a relatively small volcanic island can be.

Modern monitoring – satellites, gas sensors, GPS stations, and dense seismic networks – allows scientists to track unrest in unprecedented detail. Yet forecasting the exact timing and size of eruptions remains difficult. Instead of precise countdowns, agencies issue alert levels and hazard maps, update them as data change, and focus on reducing exposure through evacuation planning and building codes.

The 10 volcanoes below sit at the intersection of science and policy. They are not a ranked list of guaranteed disasters, but a snapshot of where many experts see heightened hazard and high stakes today.

Analysis

How Scientists Judge Volcanic Risk

Assessing whether a volcano is “likely” to erupt involves three main strands of evidence.

First is history. Stratovolcanoes like Merapi in Indonesia and Popocatépetl in Mexico erupt often, with patterns that can sometimes be linked to decades-long cycles. Caldera systems like Campi Flegrei or Yellowstone erupt less frequently but can produce much larger events.

Second is current unrest. Key warning signs include ground uplift, earthquake swarms, changes in gas emissions, and heating of crater lakes or hot springs. At Campi Flegrei, for example, the ground has been rising for years and seismic activity has surged, prompting hazard reassessments and civil-defense exercises around Naples.

Third is exposure. A moderate eruption near a megacity or busy air route can be more damaging than a larger event in a remote region. Mount Rainier’s steep, ice-covered slopes and proximity to the Seattle–Tacoma region make it one of the most worrying volcanoes in the United States, primarily because of the risk of huge mudflows, known as lahars.

With those principles in mind, the following 10 volcanoes are widely viewed as among the most important to watch over the coming years.

The 10 Most Closely Watched Volcanoes

1. Campi Flegrei (Italy)
   West of Naples, Campi Flegrei is a vast caldera rather than a single cone. It last erupted in 1538, but unrest has surged since the 1950s, with three major uplift episodes and a recent acceleration in earthquakes and ground deformation.Hundreds of thousands of people live within the caldera, and more than a million in the wider metro area. A small eruption would be primarily a local crisis. A larger one could blanket parts of southern Italy in ash, disrupt Mediterranean air traffic, and briefly cool regional climate.

2. Ioto / Iwo Jima (Japan)
   Ioto, better known as Iwo Jima, is a small island volcano in the western Pacific that has been rising steadily for decades. In recent years, uplift has accelerated and minor eruptions have built and destroyed offshore cones.A study a decade ago labeled it one of the world’s most dangerous volcanoes because a large eruption or flank collapse could generate a powerful tsunami in the region. While there is no sign of an imminent catastrophic event, the combination of long-term deformation and occasional explosions keeps it high on risk lists.

3. Reykjanes Peninsula (Iceland)
   Dormant for roughly 800 years, the Reykjanes Peninsula woke up in 2021 and has since produced more than a dozen fissure eruptions, most recently in mid-2025.Lava flows have repeatedly threatened the evacuated town of Grindavík and forced closures of the famous Blue Lagoon spa. So far, ash production has been limited and flights at Keflavík airport have continued. The larger risk lies in the possibility of a more ash-rich eruption or a shift to a different part of the peninsula closer to key infrastructure, which could disrupt North Atlantic air routes and Iceland’s tourism-dependent economy.

4. Nevado del Ruiz (Colombia)
   Nevado del Ruiz is infamous for its 1985 eruption, when small volumes of magma melted snow and ice, triggering lahars that killed more than 20,000 people in the town of Armero. Today it remains in a state of low-level unrest, with frequent ash emissions and an alert level that has oscillated between yellow and higher stages over the past decade.A similar event would again threaten communities downstream, as well as aviation over northern South America.

5. Popocatépetl (Mexico)
   Towering between Mexico City and Puebla, Popocatépetl is one of the most active volcanoes in the Americas. It produces frequent explosions, ash plumes, and lava dome collapses, punctuated by quieter periods. It appears on multiple lists of the world’s most dangerous active volcanoes because more than 20 million people live within range of ashfall, lahars, or pyroclastic flows.While civil-protection systems and evacuation plans have improved, a larger eruption would still have major consequences for air travel, agriculture, and water supplies in central Mexico.

6. Merapi (Indonesia)
   Merapi, meaning “the one who makes fire,” rises above the city of Yogyakarta on densely populated Java. It is one of Indonesia’s most active and hazardous volcanoes, producing frequent dome-building eruptions, pyroclastic flows, and ashfalls.Merapi’s eruptions tend to be smaller than super-volcano events but occur far more often, making it a chronic threat to hundreds of thousands of people. Even moderate activity can disrupt airports, highways, and rice production across central Java.

7. Taal (Philippines)
   Taal is a complex volcano set within a lake south of Manila. Its 2020 eruption sent ash over the capital and forced mass evacuations. Since then it has remained restless, with episodes of gas-rich plumes, steam explosions, and elevated sulfur dioxide emissions. Minor eruptions in 2025 have prompted renewed attention, even as the official alert level has generally stayed at 1, signaling low-level unrest. A future eruption on the scale of 2020 would again disrupt air traffic, displace tens of thousands of people, and affect agriculture and water quality in one of the Philippines’ economic heartlands.

8. Sakurajima (Japan)
   Sakurajima, in southern Japan, is a classic example of a persistently active volcano embedded in a modern city. It sits across the bay from Kagoshima, which has more than half a million residents. Sakurajima regularly produces explosions, ash plumes, and small lava flows, and it has a history of larger eruptions that blanketed the region in tephra.The main concern is not a single apocalyptic event but the cumulative impact of ash on health, infrastructure, and agriculture, alongside the low-probability risk of a larger explosive phase.

9. Mount Rainier (United States)
   In Washington State, Mount Rainier looms over the Puget Sound region. Its steep, glaciated slopes and history of gigantic lahars have led US agencies and multiple independent assessments to classify it as one of the country’s most dangerous volcanoes.There is no sign of imminent eruption, but even moderate activity could melt ice and snow, sending fast-moving mudflows down river valleys toward communities and industrial areas. The global impact would likely be more economic than climatic, centered on ports, tech infrastructure, and insurance markets in the Pacific Northwest.

10. Yellowstone Caldera (United States)
    Yellowstone is the archetypal “supervolcano,” and it attracts intense public attention. Geologically, it has produced some of the largest known eruptions on Earth, but those events are separated by hundreds of thousands of years. Current monitoring shows no evidence of magma rising toward the surface in a way that suggests a large eruption is near. The most likely future activity would be small hydrothermal explosions or minor lava flows. Even so, any escalation in unrest would trigger global media coverage, market jitters, and a wave of speculation about climate effects, underlining how intertwined geophysics and modern information networks have become.

Global Ripple Effects of a Major Eruption

While each volcano has its own personality, their potential global impacts share common threads.

Ash clouds at cruising altitudes can damage jet engines, forcing airlines to divert or cancel flights across entire regions, as happened over Europe in 2010. Sulfur-rich plumes that reach the stratosphere can form aerosols that cool the planet for a year or two, affecting crop yields and energy demand.

Large lahars and pyroclastic flows can wipe out infrastructure – ports, power plants, highways – in minutes. In highly connected economies, that damage feeds through to global supply chains, commodity prices, and insurance losses. Persistent ashfall can contaminate water supplies, overload roofs, and accelerate corrosion in machinery from farms to data centers.

Finally, the psychological impact matters. Images of red lava and towering ash plumes spread instantly on social media. Even a moderate eruption can amplify anxiety about climate, disaster preparedness, and political competence, shaping debates far from the volcano itself.

Why This Matters

The people most directly affected by these volcanoes are local residents: farmers on Java’s slopes, fishers around Taal Lake, families in Grindavík, workers in central Mexico or Colombia’s coffee region. For them, eruption risk is a daily fact of life, not an abstract concept.

Short term, a major eruption can trigger evacuations, damage homes, and cut off roads and power. It can spike food and fuel prices in nearby cities and force governments to divert resources from other priorities. Over the longer term, repeated ashfall or the perception of risk can change where people live, how land is used, and which industries thrive.

Globally, volcanoes sit alongside storms, droughts, and earthquakes as systemic risks to a tightly coupled world economy. Even when direct climate impacts are modest, disruption to aviation, shipping, and key export sectors like tourism or agriculture can ripple across borders. Iceland’s Reykjanes activity, for example, repeatedly tests how to keep a tourism-dependent economy functioning under recurring geologic stress.Reuters+1

Key developments to watch include changes in official alert levels, new evacuation drills, large uplift or seismic swarms at major calderas, and any sign of unusual ash reaching the stratosphere. Together, they signal whether a restless volcano is edging closer to a phase that could have wider consequences.

Real-World Impact

Consider a small manufacturing firm on the outskirts of Mexico City. When Popocatépetl sends ash over the capital, workers may struggle to reach the plant, roads can become slippery, and deliveries are delayed. If the airport closes, imported components and exports back up. Even without direct damage, the business faces lost orders and rising costs.

On Java, a typical low-income household near Merapi might lose crops when ash smothers rice paddies or vegetables. Livestock need extra feed and clean water. If evacuation is ordered, family members may spend weeks in temporary shelters, missing work and school. Savings, if any, are quickly exhausted.

A regional hospital in Colombia, downwind of Nevado del Ruiz, must prepare for both chronic and acute impacts. During quiet periods, fine ash can still aggravate respiratory conditions. During eruptive phases, the hospital may see sudden influxes of patients with burns, trauma, or lahar-related injuries, even as its own water supply and power are under strain.

In Iceland, a tour company built around visits to the Blue Lagoon and nearby lava fields must adapt to repeated closures. Each new eruption forces last-minute itinerary changes and refunds. Some visitors stay away; others are drawn by the spectacle. For the company, the difference between a manageable disruption and a crippling season can hinge on the precise path of a lava flow or a shift in gas emissions.

Conclusion

Earth’s 10 most closely watched volcanoes highlight a central tension of life on a dynamic planet. The same forces that build fertile soils, geothermal power, and dramatic landscapes can, under the wrong conditions, destroy towns, disrupt economies, and cool the climate.

No scientist can say exactly when Campi Flegrei might next erupt, when Reykjanes fissures will fall quiet again, or whether Nevado del Ruiz will repeat its 1985 tragedy. What can be said with confidence is that eruptions somewhere are certain – and that their consequences will be shaped as much by planning, communication, and infrastructure as by the physics of magma and ash.

Over the coming years, signals to watch include shifts in long-term unrest at major calderas, changes in volcano alert levels, new investments (or cuts) in monitoring networks, and the way governments handle evacuations and rebuilding. Those choices will determine whether the next headline-grabbing eruption becomes a global crisis – or a story of foresight paying off.