Mount Pinatubo - the impacts of a volcanic eruption in an LEDC
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On the Island of Luzon in the Philippines in South East Asia lies the volcano that is Mount Pinatubo. It is located at the plate boundary between to the Eurasian and Philippine Plate. It is one of a chain of volcanoes known as the Luzon volcanic arc, which is the result of the Oceanic Philippine plate being subducted under the lighter Continental Eurasian plate. The Volcano is slightly offset from the plate boundary as, when the Oceanic plate is subducted it is melted and forced away as molten magma by the high pressures exerted on it. It then resurfaces as the density of the molten magma becomes lower than that of the rock, and so it pushes it up through the small cracks and explodes out through a volcano.It exploded in 1991 and had some catastrophic effects, both for the people of the Philippines and the USA air force at Clarke airbase.
•847 People Killed - 300 from collapsing roofs , 100 from the mud flows known as lahars, the rest from disease in the evacuation centres including measles.
•650,000 workers lost jobs
•$700 Million Damages
•1.2million people lost homes
Electricity went off, water was contaminated, road links were destroyed, and telephone links were cut
58,000people had to be evacuated from a 30km radius of the volcano
Houses and bridges destroyed and needed replacing and airport had to be closed
Volcanic ash is blown in all directions over hundreds of KMs, smothering fields and buildings.
847 people lost their lives, 300 killed by collapsing roofs and 100 by lahars.
Heavy rainfall from Typhoon Yunga causes buildings to collapse.
Fast flowing volcanic mudflows (lahars) cause sever river bank erosion, undercut bridges etc.
1.2 million people lost their homes around the volcano and had to migrate to shanty towns in .
Farmland destroyed by falling ash and pumice, unusable for years, the 1991 harvest was destroyed and 650,000 people lost their jobs
Global cooling caused by ash in the atmosphere of 0.5°C
The management attempted
Prediction, Prevention, Aid and Monitoring
What they actually did
75,000 people were evacuated due to accurate predictions. There was no monitoring until the 3rd of April but seismometers were put into place.
The United States Geological Service helped to predict the disaster
75,000 people evacuated up to a radius of 30km. air force helicopters helped.
Alert systems put into place to warn of eruption.
Evacuation camps built for refugees.
Warning sign like gas and steam looked for. Long and short term aid organized especially from the Red Cross and the
What they could have done
Set up permanent monitoring points or use satellite images to look upon volcano site for changes in land surface.
Placed strategies for long term aid and disease control in evacuations prepared for.
Storage of medical supplies food and water in preparation for disaster.
Find out more
Research this excellent website
Read these excellent case study notes
Fantastic site on Mount Pinatubo - look at pages 2 and 3
Watch the Sulphur Dioxide cloud disperse on this movie
|Explosion at Clark Air Base||Explosion at Clark Air Base part 2|
Try this Venn Diagram exercise
Click here for full screen version
In June 1991, the second largest volcanic eruption of the twentieth century* took place on the island of Luzon in the Philippines, a mere 90 kilometers (55 miles) northwest of the capital city Manila. Up to 800 people were killed and 100,000 became homeless following the eruptions, which climaxed with nine hours of eruption on June 15, 1991. On June 15, millions of tons of sulfur dioxide were discharged into the atmosphere, resulting in a decrease in the temperature worldwide over the next few years.
Mount Pinatubo is part of a chain of composite volcanoes along the Luzon arc on the west coast of the island. The arc of volcanoes is due to the subduction of the Manila trench to the west. The volcano experienced major eruptions approximately 500, 3000, and 5500 years ago.
The events of the 1991 eruption began back in July 1990, when a magnitude 7.8 earthquake occurred 100 kilometers (62 miles) northeast of the Pinatubo region, determined to be a result of the reawakening of Mount Pinatubo. In mid-March 1991, villagers around Mount Pinatubo began feeling earthquakes and vulcanologists began to study the mountain. (Approximately 30,000 people lived on the flanks of the volcano prior to the disaster.) On April 2, small explosions from vents dusted local villages with ash. The first evacuations of 5,000 people were ordered later that month.
Earthquakes and explosions continued. On June 5, a Level 3 alert was issued for two weeks due to the possibility of a major eruption. The extrusion of a lava dome on June 7 led to the issuance of a Level 5 alert on June 9, indicating an eruption in progress. An evacuation area 20 kilometers (12.4 miles) away from the volcano was established and 25,000 people were evacuated.
The following day (June 10), Clark Air Base, a U.S. military installation near the volcano, was evacuated. The 18,000 personnel and their families were transported to Subic Bay Naval Station and most were returned to the United States. On June 12, the danger radius was extended to 30 kilometers (18.6 miles) from the volcano resulting in the total evacuation of 58,000 people.
On June 15, the climatic eruption of Mount Pinatubo began at 1:42 p.m. local time. The eruption lasted for nine hours and caused numerous large earthquakes due to the collapse of the summit of Mount Pinatubo and the creation of a caldera. The caldera reduced the peak from 1745 meters (5725 feet) to 1485 meters (4872 feet) high is 2.5 kilometers (1.5 miles) in diameter.
Unfortunately, at the time of the eruption Tropical Storm Yunya was passing 75 km (47 miles) to the northeast of Mount Pinatubo, causing a large amount of rainfall in the region. The ash that was ejected from the volcano mixed with the water vapor in the air to cause a rainfall of tephra that fell across almost the entire island of Luzon. The greatest thickness of ash deposited 33 centimeters (13 inches) approximately 10.5 km (6.5 mi) southwest of the volcano. There was 10 cm of ash covering an area of 2000 km2 (772 square miles). Most of the 200 to 800 people (accounts vary) who died during the eruption died due to the weight of the ash collapsing roofs and killing to occupants. Had Tropical Storm Yunya not been nearby, the death toll from the volcano would have been much lower.
In addition to the ash, Mount Pinatubo ejected between 15 and 30 million tons of sulfur dioxide gas. Sulfur dioxide in the atmosphere mixes with water and oxygen in the atmosphere to become sulfuric acid, which in turn triggers ozone depletion. Over 90% of the material released from the volcano was ejected during the nine hour eruption of June 15.
The eruption plume of Mount Pinatubo's various gasses and ash reached high into the atmosphere within two hours of the eruption, attaining an altitude of 34 km (21 miles) high and over 400 km (250 miles) wide. This eruption was the largest disturbance of the stratosphere since the eruption of Krakatau in 1883 (but ten times larger than Mount St. Helens in 1980). The aerosol cloud spread around the earth in two weeks and covered the planet within a year. During 1992 and 1993, the Ozone hole over Antarctica reached an unprecedented size.
The cloud over the earth reduced global temperatures. In 1992 and 1993, the average temperature in the Northern Hemisphere was reduced 0.5 to 0.6°C and the entire planet was cooled 0.4 to 0.5°C. The maximum reduction in global temperature occurred in August 1992 with a reduction of 0.73°C. The eruption is believed to have influenced such events as 1993 floods along the Mississippi river and the drought in the Sahel region of Africa. The United States experienced its third coldest and third wettest summer in 77 years during 1992.
Overall, the cooling effects of Mount Pinatubo's eruption were greater than those of the El Niño that was taking place at the time or of the greenhouse gas warming of the planet. Remarkable sunrises and sunsets were visible around the globe in the years following the eruption.
The human impacts of the disaster are staggering. In addition to the up to 800 people who lost their lives, there was almost one half of a billion dollars in property and economic damage. The economy of central Luzon was horribly disrupted. In 1991, the volcano destroyed 4,979 homes and damaged another 70,257. The following year 3,281 homes were destroyed and 3,137 were damaged. Damage following the eruption was usually caused by lahars - rain-induced torrents of volcanic debris that killed people and animals and buried homes in the months after the eruption. Additionally, a 1992 eruption in August 1992 killed 72 people.
The United States military never returned to Clark Air Base, turning over the damaged base to the Philippine government on November 26, 1991. Today, the region continues to rebuild and recover from the disaster.
These notes are aimed at students studying for Edexcel (B) Unit 5 - Hazards, though will be suitable also for people studying with different exam boards and at different levels.
They were originally submitted by wackojacko in this thread on TSR Forums.
Article by TSR User on Thursday 15 February 2018