Volcanic eruptions are one of Earth's most dramatic and violent forces of change. Not only can powerful explosive eruptions drastically alter land and water for tens of kilometres around a volcano, but tiny liquid droplets of sulphuric acid erupted into the stratosphere can change the planet's climate temporarily. Eruptions often force people living near volcanoes to abandon their land and homes. Those living farther away are likely to avoid complete destruction, but their cities and towns, crops, industrial plants, transportation systems, and electrical grids can still be damaged by tephra, ash, lahars, and flooding.
Studies of the geologic history of a volcano are generally necessary to make an assessment of the types of hazards posed by the volcano and the frequency at which these types of hazards have occurred in the past. The best way to determine the future behaviour of a volcano is by studying its past behaviour as revealed in the deposits produced by previous eruptions. This is very helpful when trying to predict an eruption for dormant volcanoes as they are most complex volcanoes to foresee an eruption for. Once this information has been collected, geologists can then make forecasts concerning what areas surrounding a volcano would be subject to the various kinds of activity should a future eruption occur. This information is then used, with knowledge about the present aspects of the volcano, to make volcanic hazards maps which can aid other scientists, government, and the public to plan for evacuations, rescue and recovery. This reduces the chance of injury and death, and may even allow time for important possessions to be kept safe. An example of prediction helping to save lives includes the evacuation of 60,000 people from the area surrounding Mount Pinatubo before it erupted in 1991. This shows that it can reduce the impacts of volcanic hazards by lessening the risk of harm.
The composition of gases emitted from volcanic vents and fumaroles often changes just prior to an eruption. In general, increases in the proportions of hydrogen chloride and sulphur dioxide are seen to increase relative to the proportion of water vapour. This is an indication that the volcano may be close to erupting and so safety precautions should be put in place. Some measures are used to divert flows of lava and other materials away from towns so that houses and businesses can be saved. For example, when Mount Etna erupted in 1983, a rubble barrier 10 metres high and 400 metres long was built on its slopes, successfully diverting lava flow. This saved the lives of hundreds of locals and prevented complete destruction of their homes and businesses. However, ash clouds can cause destruction of buildings as they may deposit ash on top of buildings thus causing them to become weighted down and so collapse. In order to tackle this issue, buildings can be strengthened so the risk of collapse decreases. These measures of preparation will be highly effective during a volcanic eruption as destruction of homes and businesses can have considerable negative social and economic impacts. Nevertheless, these measures cannot be carried out by all countries as some do not have the financial stability to invest into technology that measures gas emissions or strengthen their infrastructure. Consequently, these measures cannot be seen as an appropriate measure for all countries.
Certain factors including development level, population and timing can increase the severity of the impacts. The impacts are higher level in less developed countries as they don’t have sufficient funds to prepare for a disaster. Majority of buildings are of poor quality and so can be easily damaged or collapse. If countries such as these were to prepare for a volcanic eruption, the destruction of towns/villages would be inevitable as the infrastructure is poor. Also, economic decline is to be expected after an eruption occurs as LEDCs tend to depend on agriculture as a form of income and crops and livestock are usually destroyed during an eruption. Large populations mean that more people will affected by the eruption. As the population is bigger, there is likely to be a dense infrastructure thus increasing the likelihood of building collapse; this poses a big risk to human life. Additionally, the timing of which the eruption occurs at can make a difference of the severity of the impacts. For example, if the eruption were to occur during the night, the majority of the public would be asleep therefore not know what was happening; the risk of injury or death increase drastically. In these cases, planning and preparation will not mitigate the effects to a large extent as the lack of financial stability means that investments cannot be made to make sure the least amount damage occurs.

In 1997, the Soufriere Hills Volcano erupted in Montserrat erupted. This caused the death of 19 people and hundreds of homes to be destroyed. An extensive amount of damage occurred during the eruption amounting to £1 billion worth damage. The severity of the impacts were raised due to very little management being carried out beforehand. There was no disaster management plan created before the eruption occurred so responses were slow. The majority of infrastructure had been built in areas of risk so the eruption quickly destroyed towns and therefore increased the chances of harm done to humans. Contrastingly, before the eruption of Mount Saint Helens in 1980 occurred, a considerable amount of preparation had taken place. For example, when earthquakes began in March 1980, the USGS (United States Geological Survey) started a round-the-clock monitoring system. It included gathering seismic data and measuring the rate of bulge growth, ground temperature and sulphur dioxide gas emissions. Volcanic and seismic reports were issued daily. Although 57 people died, the evacuation of thousands of people took place before the eruption occurred which meant the number of people in safety increased. This shows that depending on how much preparation is carried out before a disaster occurs, an area may have a chance of being able to secure the safety of the public and even prevent destruction of towns.
Overall, it is clear to see that a vast amount of preparation must be carried out in order to minimise the impacts of a volcanic hazard. High levels of technology is needed to constantly keep scientists up to date about new occurrences and good, well-built infrastructure is needed so that an area doesn’t become devastated.