Emergency Management. Survey Manual. The collaborative work of scientists from the U. Clark Air Force Base that happened to be situated only 9 miles from the volcano. The program and its partners respond to volcanic unrest, build monitoring infrastructure, assess hazards and vulnerability, and improve understanding of eruptive processes and forecasting to prevent natural hazards, such as volcanic eruptions, from becoming human tragedies.
At Pinatubo, the volcanic unrest began April 2, , with a series of small steam explosions. In Manila, Dr. Punongbayan also called his friend, Dr. The seismic drum room was a maze of wires and cables; the daily drum roll of seismicity posted on the walls. With air assistance from the U. All efforts were focused on answering the questions — will Pinatubo erupt catastrophically, and when?
Volcanologists are first to admit that forecasting what a volcano will do next is a challenge. In late May, the number of seismic events under the volcano fluctuated from day-to-day. Trends in rate and character of seismicity, earthquake hypocenter locations, or other measured parameters were not conclusive in forecasting an eruption.
A software program called RSAM real-time seismic amplitude measurement , developed in to keep an eye on Mount St. Helens, helped scientists analyze seismic data to estimate the pent-up energy within Pinatubo that might indicate an imminent eruption.
The map was based on the maximum known extent of each type of deposit from past eruptions and was intended to be a worst-case scenario. The map proved to forecast closely the areas that would be devastated on June The Clark Air Base sprawled over nearly 10, acres with its western end nestled in the lush, gently rolling foothills of the Zambales Mountains—only 9 miles 14 km east of Mount Pinatubo.
At the time, the population of Clark and nearby cities of Angeles, Sapangbato, Dau and Mabalacat numbered about , Senior base officials listened to daily briefings and put together plans to evacuate. Collecting this information involves studying crystals of cooled lava after an eruption, Ewert said. This implied that emissions of water vapor and carbon dioxide—the gases that dominate emissions—were also more than scientists expected. But a whopping 17 megatons of sulfur dioxide was released by the explosion, as measured by satellite spectrometer.
This implied that large amounts of gas could accumulate as bubbles and remain in the magma chamber, Newhall explained. Because this excess gas makes an eruption more explosive, it might even be that such free gas is required for a Pinatubo-like eruption, Newhall said.
If volatiles are already in excess, they can expand immediately once the pressure drops, without any delay from diffusing through melt. Knowing that magmas can hold excess gas can help with forecasting efforts, Newhall explained. 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.
The volcanic ash was dull gray with some brown, and some of the roofs still had significant ash accumulation on top of them. A: Yunya created a real humanitarian disaster. Much of the area around there became totally uninhabitable, so many local inhabitants who could evacuate had gone to other parts of the island. The rainfall was so heavy, however, that the night before we arrived, a large group of people who remained had sheltered in a gymnasium for protection from the hurricane.
Once saturated, several feet of ash on the roof became like heavy concrete, and the roof collapsed. There were a significant number of fatalities from that. In addition, there were many structural failures off base due to the weight of the ash on buildings. The combined effect of the water and the ash was devastating.
Some of the military was redeployed to other areas, but the civilian dependents who couldn't get out on their own, had to be evacuated by us. We embarked many of these families on board the aircraft carrier and made two trips from Subic Bay south to the island of Cebu, where the Air Force was flying large transport aircraft out from an old airstrip left over from World War II. We were taking thousands of people.
Interestingly, people come with a lot of stuff, including pets! Down in the hangar bay, there are tie-down spots in the deck every 10 feet or so to secure aircraft. Many now had a dog carrier, cat carrier, or birdcage attached. The U. People had to go down periodically to comfort, feed, and clean up after them. In addition to a very unhappy Doberman giving birth to a litter of puppies under some yellow gear aircraft tows , at least one other unusual situation also stuck with me.
There were some local people who had been potentially stranded, and it appeared that a few hastily arranged marriages may have occurred. I recall a distraught young lady searching for her husband, and she didn't know his last name!
Q: Even with the success of the evacuations, there were still fatalities. The eruption disproportionately impacted the native Aeta, a small aboriginal tribe that numbered about 60, before the eruption. What can we do to protect the most vulnerable populations from events such as this? A: In the more developed world, you can improve infrastructure, right?
You don't always have those options in a lot of developing countries. So, the best you can do, I think, is to provide as much assistance is as you can both technically and on a humanitarian basis. They provide warnings and assessments in the event of a potential eruption or after one has occurred. Banner design by Bobbie Myers. Web design and layout by Carolyn Donlin.
For more information or paper copies of this fact sheet contact: U. Related Fact Sheets. What Are Volcano Hazards? See a list of other volcano-related fact sheets published by the U. Geological Survey. PDF version of this fact sheet KB. The second-largest volcanic eruption of this century, and by far the largest eruption to affect a densely populated area, occurred at Mount Pinatubo in the Philippines on June 15, The eruption produced high-speed avalanches of hot ash and gas, giant mudflows, and a cloud of volcanic ash hundreds of miles across.
The impacts of the eruption continue to this day. Precursors to the Eruptions. The Eruptions.
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