In 1985, two seismologists noticed that there was a 160km gap in the Cocos and North American Plate. Two weeks later the Mexico City earthquake occurred, measuring 7.8 on the Richter scale. The thought was that the pressure was mounting, as Cocos plate that submerged under the North American plate had no small tremors for a number of years. On September 19th 1985 at 7.17am the quake hit. The epicentre was offshore of Acapulco, 350km from Mexico City. The immediate impacts of the earthquake meant that 4,596 people lost their lives, with another 1,500 people trapped within the rubble. Around 400 buildings were destroyed, along with 700 damaged and 57 on the verge of collapsing. Among the buildings destroyed were 3 hospitals. This obviously meant that there was a shortage of doctors and nurses and nowhere for the injured to go. The knock on effects of the earthquake took a further 5,000 lives, raising the death toll to nearly 10,000. Around 50,000 people were injured and 250,000 were made homeless.
Mount Pinatubo is situated in the Philippines. The main eruption on June 15th 1991 caused a massive impact that nobody expected. However, there was previous knowledge that the volcano was ready to erupt. In August1990, Mt Pinatubo experienced its first volcanic activity in nearly 500 years due to reoccurring earth movement around 100 km away from Pinatubo. From March 1991, there were a series of events that lead one to believe that an eruption was near. After numerous earthquakes, on June 7th around 1500 earthquakes occurred under Pinatubo itself. An alert level 4 was sanctioned and people within a 20km radius of the volcano were evacuated. On the Philippine Independence day, June 12th, a 20km ash cloud could be seen above Pinatubo. On June 15th, Typhoon Yunya hit the Philippine island 100km north of Pinatubo, causing existing ash to form mudslides down the mountains. At 3.39pm the eruption began. In 9 hours a total of 90% of Pinatubo’s material was expelled into the air. The ash and dust formed a mushroom cloud 34km in the air and spread up to 400km in radius. The evacuation area increased to a radius of 40km. As a result of the eruption, around 50 lost their lives but 700 people lost their lives as a result of disease due to the amount of homeless left. The typhoon caused horrendous mudslides or lahars as the ash was up to 3m deep in some areas. The mudslides destroyed and buried many buildings and homes; around 80,000 were lost in total. The total damage was estimated at £260 million. The dust cloud that engulfed the air entered the stratosphere and encircled the globe within a year. There are reports that global temperatures were reduced by 0.5°C in the year after the eruption.
Mount St. Helens is in the state of Washington in the USA. As with the eruption of Mt. Pinatubo in 1991, there were signs that St. Helens was going to erupt. In the March of 1980, an earthquake measuring 4.1 on the Richter scale caused a small eruption at St. Helens. By early May the mountain began bulging indicating a build up of magma and an increase in pressure within the volcano. At this point the bulge was 1.5m. On the 18th May the pressure was released. An earthquake, magnitude 5 on the Richter scale caused the bulge to move forwards and downwards. The released material formed a landslide of rock, glacier and ice. This moved down the mountain to fill in Spirit Lake at the bottom of the volcano. This caused excess water to spill over the banks and cause a flood down the valley. Three minutes later the side of the volcano exploded sending out nuée ardente (volcanic debris) for 25km. Within this range every form of life, vegetation and animal, was destroyed. 61 people lost their life, mainly through the inhalation of volcanic gases and flood waters washed away railways and bridges in that area, meaning that emergency services could only access the area by air. No buildings were destroyed. The government sent over $1 billion (£600 million) on replenishing the site after the eruption by planting around 18.4 million trees and trying to bring back tourists to the area.
The Japanese are the world leaders in seismic technology. Their information and expertise obviously helped them when designing new buildings. Japan is an MEDC and where the earthquake occurred is a fairly well developed area, especially as Kobe is near Tokyo. Kobe is also a very densely populated area and as land is somewhat limited in Japan, planners tend to build upwards instead of outwards. Therefore, Kobe is a well-built area and as I said in my introduction it is buildings that kill, not earthquakes. The speed of onset was very quick, and as it was 6.00am in the morning people were taken by surprise and were stuck wherever they were. However, Mexico is an LEDC, and even though Mexico City is a very well developed area, the building laws that are in place in MEDC’s are not normally present in LEDC’s. Also the vast population of Mexico City makes it difficult for planners to build new houses for all the migrants from other regions in Mexico. Mexico City is surrounded by squatter settlements, and are mainly inhabited by migrants. Most of the settlements are unstable and, when the earthquake struck there is no doubt that most of the settlements fell down and trapped and most likely killed the people inside. Also factors like the speed of onset took people by surprise. As with Kobe, the Mexico City earthquake was early in the morning. In MEDC’s, authorities tend to build public sector buildings (especially in earthquake prone areas) earthquake proof. The 3 hospitals that were destroyed in Mexico City were not earthquake proof. However, LEDC’s do not normally have the money to spend on earthquake proofing, as money is needed elsewhere.
The Philippines are also an LEDC. The land around volcanoes tends to be used as farmland in LEDC’s, as the soil is very fertile. This does pose a risk. Luckily for the people living around Mt. Pinatubo, there was some indication of an earthquake happening. The speed of onset in both volcanic eruptions were quite slow, even though we did not know when the main eruption was going to be, we knew that volcanic activity increased so dramatically, that the tell tale signs for an eruption were there. The area around Mt St. Helens was mainly wooded land and its main function was a tourist area, whereas people lived and worked on the side and the foothills of Mt. Pinatubo. The costs in money we greater in the US, but in the Philippines the livelihoods of many people were lost. Not only were their places of work lost, but their homes too.
LEDC’s lack basic amenities. If a natural disaster occurs, then the basic sanitation that the area has are wiped away, as usually the sanitation systems are not that stable. The Philippines lost around 700 lives after the eruption of Mt. Pinatubo, mainly because the refugee camps that people are put after natural disaster have poor or in most cases no sanitation. Therefore diseases like diarrhoea and cholera are easily spread within the camp. Also the knock on affects of the Mexico City earthquake are similar to that of the Philippines, but on a larger scale and the population density is much larger in Mexico City than in the area that surrounds Mt. Pinatubo. Around 5,000 people died due to disease in Mexico City.
The factors that affect the impact of a hazard are, as I mentioned in my introduction, very important to the total number of people affected. Through my case studies, I believe that the environment in which people live is the main factor that affects the impacts that the same type of hazard has. The environment in which a hazard occurs can be an MEDC or an LEDC, and as you can see from The Philippines and Mexico City, the initial impacts might not pose a tremendous problem, it’s the organisation and impacts of the long term affects. Countries like Japan or the US do not really need to worry about refugee camps for the homeless after a natural disaster as the prediction, preparation and planning is greater, as they have the funds to spend on prediction technology and providing education to the general public.
