What are the variations in the effects and responses to volcanic activity between LEDCs and MEDCs?

MEDC Volcano Eruption

Volcano: Mount St. Helens

Location: Southwestern Washington, in the Cascade Range, USA, and North America

Date: May 18, 1980

Mt. St. Helens, located in south-western Washington about 50 miles northeast of Portland, Oregon, is one of several lofty volcanic peaks that dominate the Cascade Range of the Pacific Northwest; the range extends from Mount Garibaldi in British Columbia, Canada, to Lassen Peak in northern California. Mount St. Helens is a composite volcano. A term for steep sided, often symmetrical cones constructed of alternating layers of lava flows, ash, and other volcanic debris. Composite volcanoes tend to erupt explosively and pose considerable danger to nearby life and property. Before 1980, snow-capped, gracefully symmetrical Mount St. Helens was known as the "Fujiyama of America." Mount St. Helens, other active Cascade volcanoes, and those of Alaska form the North American segment of the circum-Pacific "Ring of Fire," a notorious zone that produces frequent, often destructive, earthquake and volcanic activity.

Washington (state USA) is one of the Pacific coast states of the United States, bordered on the north by the Canadian province of ; on the east by ; on the south by ; and on the west by the Pacific Ocean. The average population density is 27 people per sq km. (by 1990 census). Living conditions are good and Washington is called the "Evergreen State". It is in Washington that the capital city of the USA is, Washington DC.

The climactic eruption in full fury in the late morning of May 18, 1980

May 18th 1980, a Sunday, dawned bright and clear. At 7 a.m. Pacific Daylight Time (PDT), USGS volcanologist David A. Johnston, who had Saturday-night duty at an observation post about 6 miles north of the volcano, radioed in the results of some laser-beam measurements he had made moments earlier that morning. Even considering these measurements, the status of Mount St. Helens' activity that day showed no change from the pattern of the preceding month. Volcano-monitoring data--seismic, rate of bulge movement, sulphur-dioxide gas emission, and ground temperature--revealed no unusual changes that could be taken as warning signals for the catastrophe that would strike about an hour and a half later. About 20 seconds after 8:32 a.m. PDT, apparently in response to a magnitude 5.1 earthquake about 1 mile beneath the volcano, the bulged, unstable north flank of Mount St. Helens suddenly began to collapse, triggering a rapid and tragic train of events that resulted in widespread devastation and the loss of 57 people, including volcanologist Johnston and destroyed all life in an area of some 180 sq km (70 sq mi); an even wider area was covered with ash and debris. It erupted with such violence that the top of the mountain was blown off and a cloud of ash and gases was sent to an altitude of 12 miles. As a result of the eruption, the mountain's elevation was decreased from 2,950 m (9,677 ft) to 2,549 m (8,364 ft). Forest Interpreters often talk about the five main phases of the eruption. The earthquake triggered the first phase, which jarred loose the bulging north flank of the mountain. It collapsed in an enormous landslide that crashed into Spirit Lake, swept up and over Johnston Ridge and then travelled 15 miles down the Toutle River Valley. Moments after the landslide began, a lateral blast tore out of the mountain. The blast, filled with superheated gas, pulverized rock and ash, swept across the landscape, snapping off trees and levelling the forest within a 230 square mile area in a matter of minutes. Following the lateral blast, a vertical ash column formed and rose 17 miles into the sky. When the ash column reached the upper atmosphere, it was swept up by the prevailing winds and carried east. Day turned into night for some eastern Washington towns like Ritzville, where over three inches (7cm) of ash fell. Eventually, the ash spread into Idaho, Montana and even circled the globe. Traces of ash from the May 18th eruption were recorded two weeks later back in Washington State.

National Guard pilots, with the help of Air Force reservists and the Coast Guard, flew to safety 137 people, eight dogs and one boa constrictor before nightfall the first day. The ash proved a problem as the helicopter's rotors created a dust cloud so thick that pilots could not see the ground when landing. 16 helicopter crews raced to their aircraft as ash fell like fine snow. A dozen slower crews were still on the ground when an order came down cancelling further flights due to the hazard.

After refuelling at Fort Lewis, the helicopters flew to the clearer ...

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After refuelling at Fort Lewis, the helicopters flew to the clearer side of the mountain, where they established a base at Toutle. Latimer flew with Capt. Mark Edelbrock, now of Day Island. The rescue involved searching each section of the mountain, one by one. Pilots flew along ridges to keep from getting lost. Trees in the path of the blast were flattened. Further away, the trees were sandblasted clean. People in the area had to face dangerous mudflows, surging floods or at least the choking ash.

The Huey helicopters had no way to lift victims, so they had to touch down and load victims aboard. Unfortunately, the helicopters were only fitted for two passengers and sometimes needed to fit more.

In the first days, pilots who found abandoned vehicles or campsites marked the objects with bright tape. Bodies were left for later.

Worried relatives showed up at the helicopter base, which was later moved to Kelso then to Toledo. Some demanded to fly in to see whether their loved ones may have survived the blast. Latimer had the difficult task of explaining that living people were the top priority.

News reporters also were demanding, because civilian aircraft had been barred from around the mountain. As space and safety allowed, relatives and reporters were shuttled in.

Deaths: trees crushed one family as they slept in their tent, but the family dog and her pups came out alive. Several bodies were cooked by the blast with no time to react. For weeks, the pilots remained around the mountain. After the live victims were removed and the bodies sent to be buried, helicopters were used to herd elk into green areas where they could find food. As a result of the eruption, the mountain's elevation was decreased from 2,950 m (9,677 ft) to 2,549 m (8,364 ft). A National Volcano Monument was established here in 1982.

LEDC Volcano Eruption

Volcano: Mt Pinatubo

Location: Philippines, South-east Asia

Date: June 15th, 1991

Mt. Pinatubo is an active volcano in the Philippines, in the central part of the island of Luzon, at the juncture of Tarlac, Zambales, and Pampanga provinces. Mount Pinatubo is almost 90 km (55 mi) north of Manila and about 24 km (16 mi) east of Angeles. Until 1991, Mount Pinatubo was classified as inactive because it had been dormant for at least 600 years. In 1991 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 sulphur dioxide were discharged into the atmosphere, resulting in a decrease in the temperature worldwide over the next few years.

Mount Pinatubo is one of a chain of that constitute the Luzon volcanic arc. The arc parallels the west coast of Luzon and reflects along the Manila trench to the west. Mount Pinatubo is among the highest peaks in west-central Luzon. Its former summit, at 1,745 meters elevation, may have been the crest of a lava dome that formed about 500 years ago during the most recent previous major eruptive episode. The volcano's lower flanks intricately dissected and densely sheathed in tropical vegetation prior to the 1991 eruptions, were composed largely of pyroclastic deposits from voluminous, explosive prehistoric eruptions.

Before the eruption, more than 30,000 people lived in small villages on the volcano's flanks. A much larger population -- about 500,000 -- continues to live in cities and villages on broad, gently sloping alluvial fans surrounding the volcano. Clark Air Base lies to the east of the volcano, within 25 kilometres of the summit, and Subic Bay Naval Station is about 40 kilometres to the southwest.

The June 1991 eruption (of Mount Pinatubo) created a 2.5-kilometer-wide and filled valleys around Pinatubo with about 5.5 +/- 0.5 cubic kilometres of deposits. ... The new summit elevation of Mount Pinatubo is approximately 1,485 meters above sea level, reduced from a preeruption elevation of 1,745 meters; the elevation of the caldera lake is between 820 and 840 meters above sea level, or about 650 meters below the highest point on the new caldera rim.

Before its June 15, 1991, eruption, Mount Pinatubo consisted of a rounded, steep-sided, domelike mass that rose about 700 meters above a broad, gently sloping, deeply dissected apron of pyroclastic and epiclastic materials.

Ten times larger than the eruption of , Pinatubo's eruption threatened the lives of a million people. A giant ash cloud rose 35 kilometres into the sky and hot blasts seared the countryside, but a more serious disaster was averted by timely, accurate warnings. Philippine authorities were able to evacuate 60,000 people from the slopes and valleys, and the American military evacuated 18,000 personnel and their dependents from Clark Air Base below the mountain -- thus saving many thousands of lives and an estimated billion dollars in property and making this the most successful case of volcanic hazards mitigation in history.

The climactic (1991) eruption destroyed the volcano's original summit. In its place is a 2-kilometer-diameter , the centre of which is offset 1 kilometre northward from the pre-eruption summit. The caldera probably formed from collapse of the volcano's summit on June 15, during the period of abundant large earthquakes in response to withdrawal of a large volume of magma from the reservoir beneath the volcano. Tephra-fall deposits 5 centimetres or more thick covered a land area of about 4,000 square kilometres surrounding Pinatubo. These deposits buried crops, and the weight of the rain-saturated tephra, no doubt with assistance from repeated intense seismic shaking and buffeting by wind, caused numerous roofs to collapse in the Philippine communities around the volcano and on the two large U.S. military bases. More than 300 people died during the eruption, most of them from collapsing roofs. Without typhoon Yunya, the death toll might have been far smaller. The typhoon brought heavy rain, which saturated the accumulating tephra, and strong winds that contributed to the widespread dispersal of tephra falling from the broad stratospheric eruption cloud.

In June and July of 1991, the volcano erupted several times, throwing millions of tons of ash and other volcanic material over 15,000 m (almost 50,000 ft) into the atmosphere. Much of this volcanic material spread around the world in the upper atmosphere. Locally, the ash reached a depth of more than 3 m (10 ft). Heavy tropical rains turned the ash to mud and triggered massive mudslides. By late August 1991 it was estimated that 550 people had died because of the eruption and its aftermath. In addition, more than 650,000 people had lost their livelihood, and 100,000 hectares (almost 250,000 acres) of agricultural land had been devastated. A further eruption in August 1992 caused more destruction. Mount Pinatubo is now about 1,760 m (5,770 ft) high.

Final Conclusions

There is no way of measuring volcanoes or measuring greater impact between two eruptions. However, from the research presented, it seems that the eruption of Mt Pinatubo in 1991 had greater impact. As well as claiming considerably more lives as Mt St Helens took only 57 and Mt Pinatubo up to 800 Mt Pinatubo had a lot more after-effects that effected many more and made 100,00 homeless. Mt St Helens wasn’t as near to densely populated areas and the volcano had a far less eventful eruption than Mt Pinatubo that corresponded with a typhoon. Mt Pinatubo had far more after effects such as the release of sulphur into the atmosphere and the mud slides from the ash and tropical rains.

Mt Pinatubo, the volcano that had the greater impact was in a LEDC country, the Philippines. It is quite possible that Mt Pinatubo’s impact might not have been so great had the country been more economically developed and had been able to prepare and carry out effective rescue operations like Mt St Helens. People in MEDCs like America are generally better educated and more equipped for the risk a volcano poses and the people living near Mt Pinatubo may not have realised the threat of the volcano and that could have contributed to the loss of lives.

MEDCs will have better educated people and more scientific methods of predicting and warning of a coming eruption, and the people who are able to carry out and maximise a rescue operation. Whereas in an LEDC, they may not have the money or facilities to rescue or minimise life or damage loss so eruptions occurring in LEDCs will undoubtedly have the bigger impact due to lack of preparation and money to carry to prevent of mend damage from the eruption.