2025’s Volcanic Boom: Global Eruptions and Air Impacts

Introduction

In 2025, the world saw a spectacular increase in volcanic activity, with 63 confirmed eruptions from 58 different volcanoes, of which 21 started this year. Many of these eruptions continued well into December, including Kīlauea in Hawaii and Semeru in Indonesia, underlining Earth's continued geological restlessness. The movement of tectonic plates influences the heightened activity; several subduction zones along, and especially surrounding, the so-called Pacific Ring of Fire push magma upwards, sometimes explosively. Typically, there are between 50 and 70 eruptions in any given year, but 2025 outpaced those projections because seismic swarms and magma buildup accelerated across high-volcano areas such as Indonesia (107 Holocene volcanoes), the United States (165), Japan (120), and Russia (114). No particular climatic influence of the El Niño type fully accounted for this increase; instead, stress from plate interaction provided the propellant for this wave, as documented in weekly reports tracking 20 or more active sites throughout the year.​

A Simple Timeline of the Eruption Wave

The year's eruptions unfolded progressively across months, starting in January with Poas in Costa Rica exploding on the 5th, spewing lava and ash plumes, followed by Telica in Nicaragua erupting twice in January and February, and Purace in Colombia sending ash clouds over the Andes in a VEI 2 event. Lewotolok in Indonesia also struck early with a fatal ashfall that blanketed nearby villages. By February and March, the Atka Volcanic Complex in Alaska ignited on February 20, while Ulawun in Papua New Guinea lofted ash as high as 10 kilometres by late March, and Raung in Indonesia began its daily plumes. April brought a surge, with Klyuchevskoy in Russia producing massive ash and lava flows, and Bulusan in the Philippines phreatically erupting with steam and ash. Midyear heated up further when on April 30, Karymsky in Russia started; Krasheninnikov awoke after centuries in early August; and Dempo in Indonesia produced plumes up to 5 kilometres high. At the end of the year, Kirishimayama in Japan started on June 22; Reykjanes flared again in July; Sabancaya in Peru kicked off on September 13 and continued; Semeru unleashed pyroclastic flows on November 19; and on December 6, Kīlauea reached Episode 38 with towering fountains. Through September, 44 volcanoes were still active, blending newcomers like Telica with long-running ones like Semeru since 2019.​

Which Eruptions Pumped Out the Most SO₂?

Of these, several stood out for their substantial SO₂ emissions, the key gas that converts to vog or volcanic smog and fine particles affecting air far and wide. Klyuchevskoy in Russia produced enormous SO₂ clouds during its April-to-August activity, visible via satellite over Kamchatka and among the year's highest totals. Semeru in Indonesia followed closely, with its November pyroclastic events and persistent daily plumes releasing heavy SO₂ loads that drifted thousands of kilometers. Ulawun in Papua New Guinea contributed significantly by carrying dense SO₂-rich ash to high altitude, while Raung in Indonesia maintained steady daily outputs impacting Southeast Asia. Kīlauea in Hawaii pumped out vog during episodic fountains, notably in December's Episode 38, while Reykjanes in Iceland sent SO2 toward Europe during its multiple bursts. Others, like Sabancaya in Peru, with 3-kilometer plumes, and Kirishimayama, added to the tally, as captured by Sentinel-5P satellite observations, underlining how these emitters dominated 2025's gas budget.

How Volcanoes Wrecked Local Air and Land

Locally, the eruptions ravaged air quality and environments, pushing the Air Quality Index into hazardous territory, often surpassing 300, with PM_2.5 and PM₁₀ levels far exceeding the World Health Organisation's daily limit of 15 micrograms per cubic meter. Semeru's November 19 pyroclastic density currents burnt landscapes 7 to 8.5 kilometres down the southeast flank, while day-to-day ash plumes of 400 to 900 meters and rain-elicited lahars destroyed 204 hectares of farmland and homes, forcing the evacuation of 300 residents amidst choking vog where SO₂ formed irritating particulates. At Kīlauea, the Hawaii Department of Health issued advisories about vog, which can cause respiratory irritation and headaches. It exacerbated asthma as the gas fanned out across the island. In Indonesia, early ashfall from Lewotolok proved deadly and created prolonged haze, while Raung and Dempo plumes fostered regional vog. The landscapes that suffered include: ash-smothered crops and sterilised soils; acid rain derived from SO₂, withered vegetation, and contaminated water sources; pyroclastics demolishing structures; and mudflows inundating communities. Sensors like PurpleAir documented sharp PM_2.5 spikes immediately after blasts, supporting real-time hazard tracking.​​

Global Air Quality Shake-Up: PM_2.5 Trends in 2025

On a global scale, while no eruption rivalled the stratospheric might of past giants like Pinatubo, the collective output subtly elevated PM_2.5 trends by 5 to 10 per cent along prevailing wind paths, layering volcanic aerosols over urban pollution. Ash and SO₂ from leaders like Semeru and Kīlauea traversed oceans via jet streams, detectable by satellites, with Ring of Fire activity compounding city smog in Southeast Asia, the Pacific, and beyond, for instance, ash from an Ethiopian event reached India without drastically altering Delhi's baseline but adding to the particulate load. Historical comparisons to Mount St. Helens, where PM₁₀ hit 50 to 570 micrograms per cubic meter nearby, echoed in 2025's regional hotspots like Kamchatka, Hawaii, and Indonesia. However, no massive stratospheric plume caused planetary cooling. Health consequences rippled outward: near sites, respiratory illnesses like bronchitis and asthma attacks surged, with fine particles penetrating deep into lungs and raising cardiovascular risks for children, the elderly, and those with preconditions. Aviation faced repeated groundings due to ash clouds, tourism in places like Hawaii and Iceland declined, and ecosystems grappled with barren ground, acidified oceans from submarine events like the Ioto eruption in Japan, and wildlife losses from fallout. Despite this, volcanic soils have historically enriched fertility, and sites like Reykjanes offer geothermal benefits amid the turmoil.

Why Emergency Plans Save Lives Near Volcanoes

Early warning systems that send alerts through apps about earthquakes, gas surges, and ground deformation mark the beginning of comprehensive emergency action plans for communities living around one of Earth's approximately 1,273 Holocene volcanoes, concentrated in the Ring of Fire. The plans are not complete without very clearly demarcated evacuation zones, such as the 5-to-10-kilometer rings used in Semeru, equipping every household with N95 masks, goggles, sealed food, and water to sustain ash storms and lahar events signalled by sirens. Community drills, such as those held regularly in Hawaii to manage vog, establish habits that help people respond calmly in a disaster, while respirator-stocking authorities coordinate NGO assistance for rapid relief after any eruption, always prioritising the most vulnerable, namely the young, old, and infirm. This preparation equips people to survive an eruption and bounce back quickly, transforming nature's fury into a story of human resilience. With 44 volcanoes still active into late 2025, proactive preparedness has ensured swift recovery.

Everyday Lessons from the Chaos:

These volcanic events of 2025 reveal the profound duality of volcanoes, magnificent architects of fertile landscapes that have sustained civilizations for millennia, yet also periodic harbingers of disruption through ash, gas, and flows that test human resilience, particularly in densely populated centers like Indonesia, Japan, and the Philippines, where millions live in the shadow of these giants. Amid the chaos, advancements in monitoring emerged as a beacon of hope, with USGS tiltmeters and seismographs providing precise forecasts for Kīlauea's episodic fountains, enabling timely evacuations and safety measures. As we reflect on a year of 63 eruptions that reshaped skies and soils worldwide, the true takeaway lies in embracing this balance: harnessing volcanic energy for geothermal power and enriched farmlands, while fortifying communities with knowledge and preparation to turn potential tragedy into triumph. In an era of heightened activity, staying vigilant not only safeguards the present but paves the way for a future where humanity coexists harmoniously with Earth's fiery heartbeat.

A Collective Responsibility

In this modern age, air quality is everyone's responsibility. Each action we take can contribute to a healthier planet. Planting trees, choosing public transportation, or supporting local clean air initiatives can make a difference. Awareness is the first step toward change.

Join us in advocating for cleaner air. Together, we can help nature regain its voice.

Let’s work together to ensure our world thrives in harmony with nature.