Discuss the view that the impact of volcanic hazards depends primarily on physical factors. (40 marks)
Volcanic events vary in size frequency and type around the world but it can be argued that these physical factors cause the greatest impact as they are uncontrollable and create the ‘initial’ impact which we can only manage and are therefore what causes the impact. On the other hand it could be said that there are many factors which affect the impacts, both human and physical.
As stated it could be argued that physical factors are what the impact of volcanic events depends primarily on, because these are the factors behind the event. The eruption of Iceland for example in 2010 had 2 phases both physically very different. On March 20th the first eruption began lasting for 6 weeks; it gained little interest from the rest of the worldwide media as the eruption was not dominated by explosive events and caused little impact to the rest of the world. This was due to the low viscous nature of the lava allowing trapped gas bubbles to escape, this also produced little ash. In contrast with the second phase on April 14th which caused a great impact globally, but mainly to Northern Europe. The physical factors which caused the impact to be so great was the high viscosity of the lava coupled with the fact that the volcano was ice capped, this produce vast amounts of ash (250,000m3)as melt water rapidly cooled the lava which was released straight into the jet stream, located directly above the volcano. The eruption measured 4 on the Volcano explosivety index, and the ahs was of a fine glassy consistency, this resulted in the force of the eruption able to project the material 27,000ft into the atmosphere which was then able to travel an extremely large distance (3000miles) over northern Europe. The impact of this was mainly economic closing airports in 14 nations for 6 days (14th-20th) costing the UK airline industry £10 million per day. As well as having wider effects on the developing world who could not sell their produce due to flights being grounded, consequently some businesses went out of business, arguably a result of the physical factor of the nature of the eruption.
Further to this volcanic eruptions also differ in frequency, length and magnitude as well as simply nature. The eruption of Mt. Etna in Sicily could be deemed to be ongoing as and eruption has been seen every year since 2001. Although these tend to have more of a localised impact due to the uncharacteristic low viscous nature of the lava, despite the volcanism being a result of subduction activity. It was this feature which caused the 1991 eruption to last for 2 years as the lava was able to travel a large distance threatening a considerable population on Etnas slopes and the town of Zafferana. Magnitude is another factor regarding the impact of volcanic events, the eruption of Mt. St. Helens on May 18th 1980 was measured as a 6 on the VEI it produced a plume of ash that rose 17km high. However, its real destructive nature came as a result of its lateral blast, which was both unexpected and deadly killing 40 people. The landslide was the largest recorded in human history and a result of the high viscosity lava which solidified and blocked the vent. All three eruptions were the result of a different underlying physical makeup that being the type of plate boundary, lava type and surface interactions. It can therefore be argued that it is the unique physical nature of each event which causes the impact.
However, I believe it is human factors such as population density, land use and infrastructure which exacerbate the initial impact and cause an event to become a natural disaster. During the eruption of Nevado del Ruiz in Columbia on November 13th 1985 4 large lahars were created by the mixing of ash and sediments with melt water from the melted glacier atop the volcano. The lahars raced down river valleys (at 60km/h) that provided a natural path towards settlement of whichmuch of the land had been cleared for agriculture providing little resistance. All 6 river valleys were filled, where nuch of the population was located as it provided as a means for travel. In some places they reached 50m wide and grown to almost 4 times their original volume. They engulfed the town of Amero which was located in the Lagurilla river valley killing more than 20,000 of the 29,000 inhabitants. The second lahar descended through the Chinchina river valley killing around 1,800 people and destroying 400 homes. This was the most destructive force of the eruption as it mixed with pyroclastic flows, in total killing around 23,000 people. If proper adherence to warning and land use and hazard mapping had been implemented more lives may have been saved.
Another factor which exacerbated the impact of volcanic events is preparedness. Although eruptions are essentially impossible to predict it is possible to estimate the level of danger and eruption may pose with adequate monitoring. The Chaiten eruption on May 2nd 2008 came as a surprise to inhabitants of the town of Chaiten, situated only 10km south of the volcano. Previous eruption records had shown the volcano to be a threat however, due to the length of time it has lain dormant (9000 years) it was not considered an active one. Chile only has one volcano observatory for a region that is very active in activity, prior to the eruption small scale seismic activity was observed. Although no warning of an imminent eruption was given the Chilean army and Navy evacuated 4000 residents of the town (with only one death caused by shock). This was due to the frequent nature of volcanic threats in the region, and although initially unprepared the government was able to mitigate the impact by quick and decisive action.
The ability for a government to provide aid following a natural disaster is also a factor which can both negate or heighten the impact. In response to the Nevado del Ruiz eruption the government sent relief workers to help with recovery however, relief workers took 12 hours to reach the town of Amero, by which time many victims who had survived the initial effects were dead. Added to this many workers lacked basic rescue materials such as shovels and tools due to insufficient provisions hindering relief efforts. In response to the Soufriere Hills eruption on Montserrat in July 1995 the infrastructure inadequacies and lack of, made communications difficult and aid hard to obtain. Although Montserrat is a UK colony it lacks many UK standards, during the eruption 50% of the water supply network was destroyed and it took days for international aid to arrive to relieve this. Some aid was also inappropriate and Montserrat now relies on diesel generators which put it in a difficult position for future development with rising fuel prices and inefficient energy production. In comparison with this eruption on Mt. Etna prompted the Italian government to provide $8 million in tax breaks to villagers following the 2002 eruption, indication that although a lack of or inadequacy in providing aid can be detrimental factor to the impact of such events it can also be a mitigating factor.
Lastly management is perhaps the most important human factor with regards to reducing or in some cases increasing the impact felt. During the 1991-1993 eruptions of Mt. Etna the town of Zafferana was threatened by a lava flow. The Italian government initially constructed earth and rock barriers to divert the flow but this failed to work. Explosives were then used to break up a very efficient lava tube system that had carried the lava 7km down slope which was successful in 1993. Only one house was destroyed a few hundred metres from the towns boundary. Again in 2002 earth barriers were constructed by the Italian government’s heavy earth lifting equipment which successfully stopped a lava flow destroying the tourist station and Refugio Saffarenza. Mt. Etna has constant sophisticated management schemes in comparison with Nevado Del Ruiz which had no permanent monitoring. Although geologists and other experts had warned of imminent eruptions which the Columbian authorities had chose not to convey the severity of to its people. Many victims had stayed in their homes as instructed. The event was a foreseeable catastrophe exacerbated by the unawareness of the volcanoes destructive history.
Overall the impact of volcanic events is dependent on both physical and human factors, it could be said that the larger the initial event the greater it is overall. However it is considerably made worse with the greater level of human factors that add to this impact. As there is nothing we as humans can do to prevent these events and much more to prepare and avoid them the emphasis is on impact should be aimed at humans seeking to cause it as little as possible, and not take for granted the physical factors which drive them and are much larger on a whole.
Note: This took me 1 hour 10 mins to write in exam conditions (hand written originally) I got marked 37/40
