By Saini Samim, Hayden Dalton, and Valerie Shayne Olfindo

At the start of July 2026, the Philippine Institute of Volcanology and Seismology (Phivolcs) recorded three distinct, short-lived explosions at Taal Volcano in under five minutes. The event propelled a column of ash and steam approximately 1.2 km into the air. Despite the dramatic display, the eruption caused minimal disruption, and the volcano has remained at Alert Level 1, classified as "low-level unrest."

On July 21, Phivolcs reported yet another eruption — the fourth that month. Data confirmed similar minor phreatomagmatic eruptions on July 12, 16, and 17. While these events may appear minor, they offer scientists critical insights into volcanic behavior and underscore why even small bursts of activity demand careful scrutiny.

A History of Destructive Eruptions

Taal Volcano is located in Batangas Province, roughly 60 km south of Manila. The active volcano occupies Volcano Island within Taal Lake — itself a large caldera formed by prehistoric eruptions — creating one of the world's most striking geological formations: an island within a lake on an island within a lake. It is one of the Philippines' 24 active volcanoes and sits within a region home to several million residents. It ranks among the country's most closely monitored volcanic systems and holds the distinction of being one of only 16 Decade Volcanoes worldwide — a designation for volcanoes with histories of large, destructive eruptions and significant risk to nearby populations. Other Decade Volcanoes include Mount Etna in Italy and Mount Rainier in the United States.

Taal's eruptive record stretches back millennia. In January 2020, the volcano sent ash plumes more than 15 km into the atmosphere, triggering evacuations of hundreds of thousands of people, disrupting air travel, and blanketing much of Luzon in volcanic ash. That event marked Taal's largest eruption since 1977. The 2020 eruption also highlighted the cascading economic impacts of volcanic events in the Philippines: agricultural damage in surrounding provinces displaced livelihoods and disrupted supply chains for weeks.

Scientists have identified evidence of numerous earlier eruptions dating back approximately 670,000 years, including a particularly destructive eruption in 1754 that buried and displaced entire towns. This history explains why even relatively modest bursts of activity from Taal command intense scientific attention. The Philippines' experience with catastrophic eruptions is not limited to Taal: the 1991 Mount Pinatubo eruption, one of the largest of the 20th century, injected vast quantities of aerosols into the stratosphere and caused global temperatures to dip temporarily, demonstrating how Philippine volcanoes can have far-reaching consequences beyond their immediate vicinity.

Two Types of Eruptions

Since the major explosive eruption of 2020, Taal has intermittently produced minor eruptions. From the beginning of 2026 through July, Phivolcs recorded 18 isolated eruptive events at the volcano — though not the kind typically associated with volcanic activity in the public imagination.

When picturing a volcanic eruption, most people envision rivers of lava or towering ash columns blasted high into the atmosphere. However, not all eruptions unfold that way. Some are driven by the interaction between water and hot rock or magma beneath the surface, producing explosive bursts of steam rather than lava flows.

Eight of Taal's eruptions this year have been classified as "phreatic" eruptions — essentially steam explosions. These occur when groundwater or lake water is heated so rapidly by hot rock or magma that it flashes into steam, fracturing the surrounding rock. Little to no new magma reaches the surface during such events.

The remaining eruptions have been "phreatomagmatic," occurring when rising magma comes into direct contact with water. The rapid expansion of steam shatters both the magma and surrounding rock into fine ash, making these eruptions generally more energetic than purely phreatic explosions. The fine ash generated can pose respiratory hazards to nearby communities and, in larger events, endanger aircraft by damaging jet engines — a risk that prompted the establishment of international Volcanic Ash Advisory Centers after the 2010 Eyjafjallajökull eruption in Iceland grounded flights across much of Europe.

Taal is particularly susceptible to both phreatic and phreatomagmatic eruptions because its active crater contains a lake, providing a ready water source to interact with rising magma. This makes steam-driven explosions a hallmark of the volcano's behavior. Distinguishing between phreatic and phreatomagmatic activity provides volcanologists with critical information about subsurface processes, helping them assess how the volcanic system is evolving and whether associated hazards may be shifting.

Why Close Monitoring Matters

Taal is one of many active volcanoes in the Philippines, a country situated on the Pacific Ring of Fire — a belt of volcanoes encircling much of the Pacific Ocean where multiple tectonic plates converge. The Philippines uses a five-tier volcano alert system, from Level 1 (low-level unrest) to Level 5 (hazardous explosive eruption in progress), and Phivolcs adjusts the rating as monitoring data evolve.

While volcanologists cannot precisely predict when a volcano will erupt, systematic monitoring can yield early warning signs that a volcanic system is changing. Scientists track the frequency and intensity of earthquakes, deploy satellites and GPS instruments to detect subtle ground deformation, measure volcanic gas emissions such as sulphur dioxide and carbon dioxide, and monitor changes in crater lake temperature and chemistry. Phivolcs operates a network of seismic stations, gas sensors, and thermal cameras around Taal, making it one of the most densely instrumented volcanoes in Southeast Asia.

Together, these observations help determine whether magma is ascending, pressure is building, or the overall level of volcanic hazard is shifting. However, certain forms of volcanic activity — particularly phreatic eruptions — remain extremely difficult to detect and forecast, as they are not always preceded by large volumes of magma rising toward the surface.

This challenge was tragically underscored by the 2019 Whakaari White Island eruption in Aotearoa New Zealand, which caused multiple fatalities and severe burn injuries among tourists visiting the island. In the aftermath of that disaster, volcanologists have intensified efforts to identify warning signs of imminent phreatic or "hydrothermal" eruptions more reliably.

Taal's most recent eruption caused little disruption, but it contributed another valuable data point to the broader effort to understand these complex magmatic systems. For volcanologists, each eruption — no matter how small — yields additional clues that help refine future hazard assessments and strengthen preparedness for communities living in the shadow of active volcanoes.

The Conversation via Reuters Connect

Saini Samim is a postdoctoral research fellow at the University of Melbourne. Hayden Dalton is a lecturer in Geoscience at the University of Melbourne. Valerie Shayne Olfindo is a PhD candidate at the School of the Environment, University of Queensland.