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Managing Volcanic Hazards
Test your knowledge of volcanoes in this quiz.

Managing Volcanic Hazards

Volcanic eruptions are hazards resulting from tectonic activity. During your GCSE geography lessons, you will have made a case study of a volcanic eruption. For your exams, you need to know what causes an eruption, the primary and secondary effects and that these can be positive as well as negative. You should also know and understand the immediate and long term responses and how volcanic eruptions are monitored. Millions of people throughout the world live close to volcanoes and benefit from them. Managing the hazards from volcanoes is necessary to their survival.

The Earth's crust is extremely thin compared to the overall size of the planet and is cracked into large plates. These plates move around, driven by convection currents in the Earth's mantle.

As they move, they collide, move apart and slide sideways past each other, creating earthquakes and volcanoes close to their boundaries. When the volcanoes erupt, the materials produced by the eruption can be hazardous.

There are several different types of volcano, two common types are shield and composite cone. Eruptions from shield volcanoes tend to be less explosive than from composite cone volcanoes because the lava is much less viscous. Ash is erupted and is carried high into the air by the rising air above the volcano. This is a hazard to aviation and flights are sometimes diverted or even cancelled when there is a large eruption beneath an air corridor. As the lava cools and solidifies, new crust is formed. Where this happens on land, the lavas will eventually weather, forming mineral-rich soils.

Eruptions occur when magma reaches the surface of the Earth. Magma is intensely hot and the heat is transferred into the rocks around the rising magma. Any groundwater that is circulating will be heated and where the water reaches the surface, it becomes a hot spring. Some of these are cool enough to supply warm water for public baths, something that was noticed and often used by the Roman Empire. During the eighteenth and nineteenth centuries, hot springs became very popular with the middle and upper classes who believed that the mineral-rich warm water had health-giving properties. In the UK, although there are currently no volcanoes, heat from magma deep in the crust still warms groundwater in some places.

Volcanic eruptions are entirely unpredictable and the best that monitoring can do is to alert the authorities shortly before an eruption occurs. Volcanoes that are close to centres of populations are the most-closely monitored, for example Mt. Etna in Sicily. Scientists look for clusters of small earthquakes (caused by the magma pushing its way upwards through the crust), an increase in temperature around the volcano and any sudden increase in gases given off by the volcano. The only effective management for most eruptions is to evacuate the area. In MEDCs, the emergency services can be mobilised very quickly, so medical aid and shelter can reach the stricken area soon after the eruption. In LEDCs, it takes a lot longer. Often the bulk of the aid will be donated by MEDCs which takes time to organise. That means more people are likely to die, either as a result of the eruption, from untreated injuries, infections or even disease.

There are several reasons why communities in LEDCs are more vulnerable than those in MEDCs. Which of the following statements is false?
Volcanoes in LEDCs erupt less often than in MEDCs so they are not as used to dealing with eruptions
Active volcanoes are often better monitored
The government can issue warnings via TV and radio a few days before an eruption
Fewer people have motor vehicles and the roads are often a lot worse in LEDCs
Rural populations in LEDCs have less access to broadcast media and so warnings may not reach them before the eruption occurs
What is the most effective way to protect a population during a volcanic eruption?
Provide specially reinforced umbrellas to protect them from the volcanic bombs
Build a large wall around the centre of population
Provide volcano suits to protect them from the heat
The only way that a population can be protected is by evacuation. If the lava from an eruption is of the viscous (thick and slow moving) type then it may be possible to build a wall from pre-cast concrete blocks to deflect it, however, there are still the other dangers to contend with
In MEDCs, people living near volcanoes are generally better prepared for an eruption. Which of the following is the most likely reason?
People in MEDCs are wealthier and can buy homes that are built to withstand a volcanic eruption
People in LEDCs have lower literacy skills
People in MEDCs have more leisure time and can spend more time getting fit so that they can run away from an eruption
People in LEDCs cannot afford to leave their homes during an eruption
Preparing people for a volcanic eruption includes education. That is more difficult where literacy levels are low because fewer people can read leaflets and posters
Which of the following is not a hazard from a volcano?
Lava flow
Storm surge
Ash cloud
There are other hazards too such as nuée ardentes, toxic gases and volcanic bombs
Which type of volcano is most likely to cause loss of life and property when it erupts?
Sword is not a type of volcano. The lava from shield volcanoes is much less viscous than in a composite volcano and therefore eruptions are less explosive
Some volcanoes are closely monitored for signs of an eruption. Which of the following is not an indicator that an eruption is likely to occur?
An increase in oxygen levels around the volcano indicates that magma is rising
Dozens or even hundreds of micro-earthquakes indicates that magma is rising
An increase in sulfur dioxide around the volcano as gases are released from the rising magma
Ground temperatures increase around the volcano as the red hot magma gets closer to the surface
Volcanoes emit many gases, but never oxygen
Which of the following would be classed as a secondary effect of a volcanic eruption?
Destruction of crops and livestock by flooding where volcanic ash blocks rivers
Forests destroyed by a nuée ardente
People killed by toxic gases
Lahars destroying crops and homes
A secondary effect is something that is not caused directly by the eruption. In this case, although the flooding is caused by the ash, the destruction is actually caused by the water and not the eruption
Volcanic eruptions can have a devastating effect on communities and the environment yet people still live close to volcanoes and volcanically-active areas. Which of the following is not a reason for this?
Mudflows clear areas of woodland or agriculture
When volcanic ash weathers, it releases nutrients into the soil
Underground heat
Tourists like to visit volcanoes
The heat underground can be used to generate geothermal energy, the extra nutrients in soil make them more fertile and tourism brings cash into the local economy
Why are more people likely to die when a volcanic eruption occurs in a poor country?
They don't have the technology to monitor volcanoes closely
They don't have the resources to support the populations affected
Poor communications and infrastructure make evacuation slow and inefficient
All of the above
Monitoring is not as effective as in countries that are wealthy so there is a lot less warning before an eruption occurs, taking people by surprise. Aid often needs to come in from abroad and that always takes several days to organise
Montserrat is a small island in the Caribbean and is a LEDC. A volcano on the south of the island started to give warning signs that an eruption was imminent. Two years later, the most intense eruptions occurred, however, there had been plenty of time to evacuate the population from the island. Which of the following would be classed as a long term response or result of the eruption?
Abandonment of the capital city
Building an observatory to monitor the volcano
Increased unemployment because tourists stopped visiting the island
Since the volcano has calmed down again, the tourist industry has recovered
You can find more about this topic by visiting BBC Bitesize - Volcanoes

Author:  Kev Woodward

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