🌋VolcanoAtlas

Mount Pinatubo

The Eruption That Cooled the World

Elevation

1,486 m

Last Eruption

2021

Type

Stratovolcano

Country

Philippines

Location

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Volcanic Hazards & Risk Assessment

Primary Hazards

  • Pyroclastic flows
  • Lava flows
  • Volcanic bombs and ballistics
  • Lahars and mudflows

Risk Level

Population at RiskHigh
Infrastructure RiskHigh
Aviation RiskSignificant

Geological Composition & Structure

Rock Types

Primary
Unknown
Silica Content
Varied composition

Tectonic Setting

Unknown
Intraplate setting with hotspot or regional volcanic activity.

Age & Formation

Epoch
Unknown
Evidence
Unknown

Eruption Statistics & Analysis

MetricValueGlobal RankingSignificance
Total Recorded EruptionsUnknownLowModerately active volcano
Maximum VEIVEI UnknownMinorLocal impact potential
Recent Activity5 years agoVery RecentCurrently active

Monitoring & Alert Status

Monitoring Networks

Global Volcanism Program
International eruption database

Current Status

Active
Recent volcanic activity detected. Continuous monitoring in place.

Authority Sources

Smithsonian GVP
Official volcano database

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Interesting Facts

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The 1991 eruption of Mount Pinatubo was the largest volcanic eruption to directly affect a densely populated area in the 20th century, ejecting approximately 10 km³ of material and creating a 2.5-km-wide summit caldera.

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The eruption injected approximately 17 megatons of sulfur dioxide into the stratosphere — more than any eruption since Krakatau in 1883 — lowering global temperatures by 0.5°C for two years.

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Prior to 1991, Pinatubo had no historically recorded eruptions and was so obscure that many local residents did not know they lived near an active volcano.

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The successful monitoring and evacuation effort is credited with saving an estimated 5,000 to 20,000 lives, making Pinatubo the gold standard for volcanic crisis management.

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Pinatubo has produced four VEI 6 eruptions in approximately 9,500 years — a recurrence rate of one mega-eruption roughly every 2,400 years, making it one of the most consistently explosive volcanoes on Earth at this scale.

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The eruption coincided with Typhoon Yunya, whose heavy rains mixed with falling ash to collapse roofs and trigger lahars — approximately 90% of the 847 fatalities were caused by roof collapses rather than direct volcanic effects.

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Post-eruption lahars continued to devastate communities for over a decade, arguably causing more total economic damage than the eruption itself.

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The destruction of Clark Air Base and damage to Subic Bay contributed to the end of the U.S. military presence in the Philippines — the Philippine Senate voted to reject the new basing treaty just three months after the eruption.

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Lake Pinatubo, the turquoise crater lake that now fills the 1991 caldera, has become one of the most popular hiking destinations in the Philippines.

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The eruption displaced approximately 20,000 Aeta (Negrito) indigenous people from their ancestral homeland on Pinatubo's slopes — a cultural displacement from which the community has never fully recovered.

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The stratospheric aerosol cloud from the eruption contributed to record ozone depletion — the largest ozone hole ever measured up to that time was recorded over Antarctica in 1992, partly attributed to Pinatubo's emissions.

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Before the eruption, Pinatubo's summit stood at approximately 1,745 m (5,725 ft); the eruption removed more than 300 m, reducing it to the current 1,486 m (4,875 ft).

Frequently Asked Questions

Is Mount Pinatubo still active?
Yes, Mount Pinatubo is classified as an active volcano by the Philippine Institute of Volcanology and Seismology (PHIVOLCS). The most recent volcanic activity was a minor phreatic (steam-driven) event on November 30, 2021. While the volcano has been largely quiet since the catastrophic 1991 eruption, its geological record reveals four VEI 6 eruptions over the past 9,500 years — a recurrence pattern that confirms future large eruptions are certain over geological timescales. PHIVOLCS maintains continuous monitoring of seismicity, gas emissions, and the chemistry of crater Lake Pinatubo. The average interval between major eruptions is approximately 2,000–3,000 years, but the 1991 experience showed that Pinatubo can transition from apparent dormancy to catastrophic eruption in just 10 weeks.
When did Mount Pinatubo erupt?
Mount Pinatubo's most famous eruption occurred on June 15, 1991, when a VEI 6 Plinian eruption — the largest to directly affect a populated area in the 20th century — ejected approximately 10 km³ of material, lowered global temperatures by 0.5°C, and killed 847 people. Precursory activity began on April 2, 1991, with the climactic eruption occurring on June 15. Smaller post-eruption events occurred in 1992, 1993, and most recently in November 2021. Before 1991, Pinatubo had no historically recorded eruptions, though geological evidence reveals VEI 6 eruptions around 7460 BCE, 3550 BCE, and 1050 BCE, plus a VEI 5 event around 1450 CE.
How many people died in the 1991 Pinatubo eruption?
The 1991 eruption killed 847 people. Remarkably, this number would have been vastly higher — estimated at 5,000 to 20,000 — without the successful monitoring and evacuation effort conducted by PHIVOLCS and the USGS, which relocated approximately 200,000 people from the danger zone before the climactic eruption. Approximately 90% of the fatalities were caused by roof collapses as rain-saturated volcanic ash accumulated to crushing weights on structures — a consequence of the simultaneous passage of Typhoon Yunya. Direct volcanic effects (pyroclastic flows, lahars) accounted for the remaining deaths. The eruption directly affected approximately 2.1 million people and caused an estimated $710 million in damage.
How did the 1991 Pinatubo eruption affect global climate?
The 1991 eruption injected approximately 17 megatons of sulfur dioxide into the stratosphere, forming a global layer of sulfuric acid aerosols that reflected solar radiation. This reduced direct sunlight reaching Earth's surface by 5–10% and lowered average global temperatures by approximately 0.5°C over the following two years — temporarily offsetting the greenhouse warming trend. The aerosol cloud also contributed to record ozone depletion: the largest ozone hole ever measured at that time was recorded over Antarctica in 1992. The cooling effect provided climate scientists with an invaluable natural experiment, and the accuracy of climate model predictions of Pinatubo's impact increased confidence in the same models' projections of future greenhouse warming.
How tall is Mount Pinatubo?
Mount Pinatubo currently stands at 1,486 m (4,875 ft) above sea level. Before the 1991 eruption, the summit reached approximately 1,745 m (5,725 ft). The eruption removed more than 300 m (984 ft) from the summit, replacing it with a 2.5-km-wide caldera that now contains Lake Pinatubo. By Philippine standards, Pinatubo is a relatively modest peak — lower than nearby Mount Negron (1,583 m) and far shorter than Mount Mayon (2,462 m) in southeastern Luzon or Mount Apo (2,954 m), the Philippines' highest peak. The summit reduction during the 1991 eruption is comparable to the loss of 401 m from Mount St. Helens' summit in 1980.
What type of volcano is Pinatubo?
Mount Pinatubo is a stratovolcano (also called a composite volcano), built from alternating layers of lava, ash, and pyroclastic deposits. Its dominant magma composition is dacite — a silica-rich, viscous magma that traps dissolved gases and produces highly explosive eruptions. This dacitic composition is very similar to that of Mount St. Helens, and both volcanoes are capable of explosive Plinian eruptions. Before 1991, Pinatubo's pre-eruption form was a dome complex covered in dense rainforest — less classically cone-shaped than typical stratovolcanoes like Mount Mayon. The 1991 eruption created the 2.5-km-wide summit caldera that now defines the volcano's appearance.
Can you visit Mount Pinatubo?
Yes, Mount Pinatubo is one of the most popular hiking destinations in the Philippines. The standard route starts from Capas, Tarlac, where visitors register and hire accredited Aeta guides. A 4x4 vehicle navigates through the dramatic lahar landscape before reaching the trailhead, from which the hike to the crater rim takes approximately 1.5–2 hours. The turquoise crater lake is the main attraction. The best time to visit is during the dry season (November–May). Organized tours from Manila (3–4 hours by road) are widely available. The trail may be closed during the wettest months (July–September) due to flooding risks.
What happened to Clark Air Base?
Clark Air Base, one of the largest United States Air Force installations outside the continental United States, was located just 25 km east of Mount Pinatubo in Angeles City, Pampanga. The base was severely damaged by ashfall and lahars during the June 1991 eruption, with roof collapses, ash deposits of up to 15 cm, and extensive damage to aircraft, buildings, and infrastructure. Over 14,500 military personnel and their dependents had been evacuated before the climactic eruption. The destruction, combined with ongoing lahar threats and broader political considerations, contributed to the U.S. decision not to seek renewal of the basing agreement. Clark was turned over to the Philippine government in November 1991 and has since been converted into Clark International Airport and the Clark Freeport Zone.
How was the 1991 eruption successfully predicted?
The successful prediction of the 1991 Pinatubo eruption is considered the greatest achievement in volcanic hazard mitigation. After initial steam explosions on April 2, PHIVOLCS deployed seismic instruments around the volcano and the USGS sent a rapid-response team from its Volcano Crisis Assistance Team (VCAT). Over the following weeks, scientists tracked escalating seismicity (particularly long-period earthquakes indicating magma movement), rapidly increasing SO₂ gas emissions (peaking above 5,000 tonnes/day), and small phreatic explosions. They issued progressively urgent warnings using a 5-level alert system, and authorities evacuated approximately 200,000 people from a 40-km radius before the climactic June 15 eruption. This effort is estimated to have saved 5,000 to 20,000 lives.
What are lahars and why were they so devastating after Pinatubo?
Lahars are fast-moving mixtures of water, volcanic debris, and sediment — essentially volcanic mudflows with the consistency of wet concrete. The 1991 eruption deposited 5–7 km³ of loose pyroclastic material on Pinatubo's flanks, and each rainy season — particularly during typhoons — remobilized enormous volumes as lahars that buried communities, destroyed bridges, and filled river channels across central Luzon. The lahars were especially destructive because the Philippines experiences regular typhoons that deliver intense rainfall to the volcano's steep, ash-covered slopes. Post-eruption lahars continued for over a decade, arguably causing more total economic damage than the eruption itself. Major engineering projects, including the Mega Dike system, were built to protect vulnerable communities.