Mount Pinatubo’s cataclysmic eruption happened during a typhoon
The largest volcanic eruption in living memory began on June 12, 1991
Weather and geology collided in the middle of June 1991 when a typhoon swirled over one of the most powerful volcanic eruptions in living memory.
The island of Luzon dealt with two disasters at once that week. Mount Pinatubo erupted over the course of three days, culminating in a cataclysmic blast on June 15—the very same day Typhoon Yunya swept across the region.
Heavy rains and gusty winds made the effects of this powerful volcanic eruption even worse. That very eruption would go on to affect global weather patterns for months after the event.
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A hulking stratovolcano rumbles awake
Mount Pinatubo measured more than 1,700 metres high at the beginning of spring 1991 when magma began moving beneath the tree-covered stratovolcano. Hundreds of thousands of people lived near the volcano in southwestern Luzon when the earthquakes began that March.
Thousands of tiny earthquakes rattled the volcano and surrounding areas over the following three months, tremors that raised red flags for experts who understood it meant Pinatubo was waking up.
Scientists enhanced their monitoring of the volcano through the middle and late spring, formulating evacuation plans in case of a full-on eruption.
They didn’t have to wait long.
Pinatubo’s increasingly violent eruptions
Lava began gurgling out of the volcano on June 6, 1991, according to the USGS, just as a prominent bulge appeared on Pinatubo’s upper-east side. Officials began evacuations soon after, including tens of thousands of personnel from the United States’ nearby Clark Air Force Base.
Magma infused with gas—not unlike a carbonated drink—reached the surface on June 12, unleashing Mount Pinatubo’s first violent eruption. A column of ash exploded 19 kilometres into the atmosphere. Several more eruptions followed over the next two days.
A catastrophic eruption occurred on June 15, an event so powerful that the top 200+ metres of the mountain collapsed to form a new caldera. Pyroclastic flows, fast-moving plumes of searing hot ash and gas, raced down the sides of the volcano to destroy and bury anything in their path.
Ash plume causes widespread damage, alters weather patterns
The blast pushed an ash cloud 40 kilometres into the air, such an immense release that scientists found it circled the Earth several times.
Typhoon Yunya made landfall in Luzon just as Pinatubo’s mammoth eruption unfolded on June 15. Tropical downpours mixed with the ash to cause even more problems, including lahars, which are mudslides of volcanic debris.
Tremendous amounts of ash and other debris fell on nearby communities, reportedly claiming hundreds of lives as roofs collapsed under the weight of the rain-soaked ash.
Pinatubo ejected so much ash and gas into the atmosphere that meteorologists noted a measurable effect on weather patterns in the months and years following the eruption. One study found that global surface temperatures temporarily fell by 0.5°C by the middle of 1992.
Header image courtesy of the USGS.