With reference to two volcanic events that you have studied from contrasting areas of the world, compare the nature of the volcanic hazard and its impact. Mount St Helens erupted on the 18th May 1980 at 9am and is an active strata volcano Washington State USA, a MEDC. Where as on 18th July 1995, during the daytime, Montserrat, a LEDC during the day, Montserrat’s Soufrière Hills composite volcano of a height 1050m, meaning sulphur hills, dormant for centuries, erupted and produced a phreatic eruption.
The volcano is a strata volcano also.Mount St. Helens is a composite volcano which lies near to a destructive plate boundary where the small Juan de Fuca Plate is being subducted underneath the North American Plate where as the eruption in Montserrat was due to subduction, but the Atlantic tectonic plate subducts beneath the Caribbean plate. Mt St Helens went on to erupt in a Plinean style, spewing out ash and produce pyroclastic flows -currents of hot gas and ash.
The magma burst out causing large pyroclastic flow flattening vegetation and buildings for over 230 square miles (600 km²). There were volcanic Mudflows- Due to collapse of northern side mixed with ice, snow and water. These flowed many miles down the Toutle and Cowlitz Rivers. This led to 3 million m³ of material being transported 7 miles (27 km) south into Columbia River by mudflows. The actual eruption itself lasted for roughly 9 hours, of which is released much gas, such as SiO2 and also over 4km³ of rock, gas and steam exploded from the northern side of the mountain. Ash which was thrown vertically into the atmosphere was found over 15km above ground level.
The blast crater averaged about 8 miles (13 km) in radius. The Montserrat eruption was of a very similar nature and erupted into in a Plinean style. Huge pyroclastic flows were produced and also masses of ash reached the surrounding areas and left the capital, Portsmouth covered in meters of ash. The lava was spewed out at 600 mph. There was a huge difference in the impacts that each volcano had on the surrounding area and people. Soufrière Hills left 23 people dead where as Mt St Helens left a staggering 59 dead.
Montserrat’s population have had their lives completely changed. Their economic, administrative and cultural capital lies in ruins like a modern Pompeii. Jobs, schools and community activities have been disrupted. At one point 5,000 people were living in temporary shelters in the north, in some cases for over two years. The north of the island had few settlements of any size and found it difficult to cope with the influx from the south. Salem is now being repopulated and is being developed together with St John’s as new population centres.
The following are some of the problems -Plymouth contained all the main services – hospitals, banks, schools, government and many private businesses. Collapse of the tourist and rice processing industries. Unemployment has risen from 7% to 50%. Agriculture is at a standstill. Respiratory problems caused by ash. Psychological problems and discontent with relocation package.
Traffic congestion. Shortage of available building land. 70% rise in rent for accommodation. Skills shortage as people left. Compared to America, they managed to short the short term problems out very quickly and efficiently due to the fact that they have much more money compared to Montserrat. One short term effect of the Mount St. Helens eruption is that 1300 feet was blasted off the top of the mountain. This would have a great effect because that would all break up into ash and encircle the Earth, which would stop heat and light from the sun coming into the atmosphere.
Power supplies were cut off and that ash got into water supplies. Consequently, it would have led to contamination of the water and the spread of disease. 230 square miles of forest burned and got destroyed. This would have a great effect on the logging industry because there would not be as many trees for them to cut down. In addition to this it would have a great effect on wildlife as 1000s of animals’ homes would have been destroyed. It destroyed or extensively damaged over 200 homes, destroyed/ damaged 185 miles (300 km) of road and destroyed/ damaged 15 miles of railways. Airports closed (from 2days → 2 weeks).
Over a thousand commercial flights were cancelled following airport closures. Lastly, unemployment rose rapidly after eruption. Montserrat could not afford for the clear up process and most of its economy was lost due to damage of the capital city where the majority of the income is found, America’s economy took a huge blow due to the fact it spent millions on the clear up process. The total economic cost for the US was $1.1 billion.
Both countries environment took a huge blow. Effects on the Landscape due to Mt St Helens include 400 metres was blown off the top of the mountain and a one mile horse shoe-shaped crater was left that was 500m deep. Every plant and animal within 25km north of the volcano was killed – approximately 7000 animals died. Every tree within 30km of the volcano was flattened.
The water produced from melting ice and snow on top of the volcano creates mudflows, which choked rivers and killed all fish and water life. Spirit Lake was filled with mud. 12 million salmon died. The eruption also destroyed 250 homes, 47 bridges, and 15 miles of railways and 185 miles of highway. In Montserrat the eruption ruined the whole capital city, leaving it buried in meters of ash and ruined all for the fertile farming land found around the area of the volcano. There have been many floods due to ash blocking the valleys and the pyroclastic flow wiped out forests.
In conclusion the two eruptions were both of similar types of eruption yet however they both created massive problems and hazards. Both were treated very differently and destroyed many different aspects of the county.