How many eruptions has mount pinatubo had

By then, almost all aircraft had been removed from Clark and local residents had evacuated. Additional explosions occurred overnight and the morning of June Seismic activity during this period became intense. The visual display of umbrella-shaped ash clouds convinced everyone that evacuations were the right thing to do. When even more highly gas-charged magma reached Pinatubo's surface June 15, the volcano exploded.

The ash cloud rose 28 miles 40 km into the air. Volcanic ash and pumice blanketed the countryside. Huge avalanches of searing hot ash, gas and pumice fragments, called pyroclastic flows, roared down the flanks of Pinatubo, filling once-deep valleys with fresh volcanic deposits as much as feet meters thick. The eruption removed so much magma and rock from beneath the volcano that the summit collapsed to form a small caldera 1.

If the huge volcanic eruption were not enough, Typhoon Yunya moved ashore at the same time with rain and high winds. The effect was to bring ashfall to not only those areas that expected it, but also many areas including Manila and Subic Bay that did not. Fine ash fell as far away as the Indian Ocean, and satellites tracked the ash cloud as it traveled several times around the globe.

With the ashfall came darkness and the sounds of lahars rumbling down the rivers. Several smaller lahars washed through Clark, flowing across the base in enormously powerful sheets, slamming into buildings and scattering cars as if they were toys.

Nearly every bridge within 18 miles 30 km of Mount Pinatubo was destroyed. Several lowland towns were flooded or partially buried in mud. The volcanologists at the Dau command post watched monitoring stations on Pinatubo fail, destroyed by the eruption. They watched telemetry go down but then come back up — a sign that a pyroclastic flow was headed down valley and temporarily interfering with the radio links.

They moved to the back of a cinderblock structure to maybe provide a little more protection from hot gas and ash; there was nowhere else for them to go.

Fortunately, the flow stopped before it reached the building. The post-eruption landscape at Pinatubo was disorienting; familiar but at the same time, totally different. Acacia trees lay in gray heaps, trees and shrubs were covered in ash. Roofs collapsed from the tremendous stresses of wet ash and continuing earthquakes.

No matter which way one turned, everything looked the same shade of gray. Most of the deaths more than people and injuries from the eruption were from the collapse of roofs under wet heavy ash. Many of these roof failures would not have occurred if there had been no typhoon. Rain continued to create hazards over the next several years, as the volcanic deposits were remobilized into secondary mudflows.

Damage to bridges, irrigation-canal systems, roads, cropland and urban areas occurred in the wake of each significant rainfall. Scientists observed a maximum global cooling of about 1. Sunsets and sunrises were more brilliant because of the fine ash and gases high in the air.

In addition, the aerosols from the eruption had a chemical effect that reduced the density of the ozone layer in the stratosphere. Until the ozone reforms, it cannot shield that portion of Earth as effectivelyfrom the sun. More than people died during the eruption, most of them from collapsing roofs. Disease that broke out in evacuation camps and the continuing mud flows in the area caused additional deaths, bringing the total death toll to people.

For example, if a volcano has been plugged since its previous eruption yet has been continuously recharged with fresh magma and gas from depth, scientists can examine the time between its eruptions to gauge whether the volcano has accumulated enough excess gas to make it particularly explosive.

The total amount of sulfur dioxide released before and during the eruption caused the most profound effect on the stratosphere since Krakatau in The sulfuric aerosols that formed from the sulfur dioxide circled the Earth within 3 weeks and remained in the atmosphere for 3 years , reflecting enough sunlight to cool the entire planet by half a degree Celsius during that time. However, during the following winter, Europe experienced surprisingly warm temperatures.

What could be going on? This temperature gradient strengthened the Arctic Oscillation , a wind pattern circling the Arctic. The shifted jet stream allowed warm winds to flow over the Northern Hemisphere during the winter, Robock said.

Because the jet stream flows like a wave, while Europe was receiving warm air from the south, the Middle East received colder air from the north, bringing to Jerusalem the worst snowstorm in 40 years. The eruption helped scientists definitively declare that human emissions of greenhouse gases are to blame for at least the past 60—70 years of warming. Temperatures rose again once the cooling aerosols fell out of the atmosphere. Pinatubo, in a sense, served as a natural climate experiment to test and calibrate models.

Scientists plugged observed volcanic emissions into climate change models with and without anthropogenic emissions of greenhouse gases.

This observation helped climate scientists sharpen their models further, confirming that humans—and the unprecedented amounts of greenhouse gases they pump into the atmosphere every year—are to blame for the warming climate. The Intergovernmental Panel on Climate Change was able to use these newly sharpened models to further support the attribution of climate change to human activities.

Robock and other scientists agree that this kind of injection would have negative consequences. To halt global warming, humans would have to inject million tons of sulfur dioxide into the atmosphere every year—that amounts to about five Pinatubo eruptions per year. Clouds of sulfuric acid particles—created when sulfur dioxide newly injected into the stratosphere meets water—provide surfaces on which ozone-destroying chemical reactions take place.

Robock said that to halt global warming, humans would have to inject million tons of sulfur dioxide into the atmosphere every year—that amounts to about five Pinatubo eruptions per year.

Scientists generally agree that the consequences of geoengineering are too risky to attempt. Pinatubo almost overtook us. Mount Pinatubo, for now, stands relatively quiet, some meters shorter than it was before it exploded 25 years ago.

What might the next 25 years bring to Pinatubo? Time will tell. Wendel, J. Published on 09 June The authors. Any reuse without express permission from the copyright owner is prohibited. Iddris et al. Skip to content The 15 June eruption of Mount Pinatubo. Preeruption Mount Pinatubo on 9 June , viewed from the northeast.

Credit: P. Tiltmeters measure how the ground swells during volcanic unrest. Credit: USGS. Evacuation zones surrounding Mount Pinatubo, created by scientists before the 15 June eruption.

Cars and people traverse a flooded river in June after lahars wiped out bridges. Aerial view to the south of the 3-kilometer-wide Pinatubo caldera showing the start of a small explosion on 1 August