Environmental Hazards - Volcanoes Flashcards
Explain how volcanoes form at diverging (constructive) plate boundaries
- Convection currents are moving apart, as a result they drive the tectonic plates apart
- Pressure in the mantle reduces as mantle rock moves upwards at the plate boundary, this reduces the melting point of magma
- Molten magma rises up from the mantle, forming lava when it reaches the Earth’s surface
- The lava cools to form new crust which is why these types of plates are called constructive, they are building/constructing new crust
Explain how volcanoes form at convergent (destructive) plate boundaries
- Convection currents move towards each other at the edge of two plates, these two plates also move towards one another
- When two plates of different densities move towards each other i.e. an oceanic and continental plate, the heavier plate (oceanic) will sink down underneath lighter one (continental) and melt into the mantle
- The two plates rub against each other, which creates
a huge amount of friction, this friction releases heat - As the oceanic plate sinks and melts into the mantle, the pressure in the mantle decreases
- Gas bubbles created by friction, the heat and the changing pressure as well as by the plankton on the oceanic plate releasing methane as the plankton are heated, magma rises to the surface creating explosive volcanic eruption, often they eject pyroclastic flows.
- Called destructive as the edge of oceanic plate is destroyed
Explain how volcanoes form at hot spots and hot plumes
- Hot plumes are stationary upwellings of unusually hot molten rock in the mantle
- Convection causes the hot molten rock to rise up to the base of the crust
- Reduced pressure encourages the melting of areas of the crust at the hot plume
- The point at where this occurs on the crust is known as a hot spot
- Volcanoes form on the ocean bed or the land surface at the point on the crust the hot spot is located
What are the advantages of living in a volcanic area
Geothermal heating - Volcanoes provide geothermal energy, because the crust is thinner in volcanic regions the mantle is able to heat underground water supplies. This can be piped into homes and industries to provide cheap heating
Sulfur mining - Volcanoes release minerals such as sulphur which are used in industry. This is mined on the sides of volcanoes. Mining sulphur in countries such as
Indonesia provides unskilled workers with much higher wages than alternative jobs because it is very dangerous work
Tourism - Volcanoes are beautiful sites, making them popular places for tourists to go to. They provide jobs in hotels, restaurants and gift shops
Explain the problems created by volcanic products
Pyroclastic flow - when they mix with rain or glacial meltwater they can create lahars. When they move they sweep away everything they come into contact with such as buildings, people, animals, trees, bridges and roads. When they settle they bury the landscape and all objects in a thick layer of mud that sets like concrete
Ash - It is highly abrasive, and when it is inhaled the fine ash particles can scar lungs which causes permanent damage. It can also damage eyesight and could permanently damage sight
Lava - It very hot so can melt road surfaces made of asphalt releasing toxic fumes. When lava comes into contact with vegetation it can create explosive methane gas
Lava bombs - They are generally larger than 64 mm and will damage or crush any buildings or vehicles they land on
Toxic gases - can kill people and livestock
What equipment can be used to predict a volcanic eruption
- Geothermal imaging
- GPS, Satellites and drones
- Tilt meter
- Gas detector
Explain how gas detectors can predict a volcanic eruption
Before a volcano erupts they will often give off different gases. Gas detectors can tell volcanologists if volcanoes are giving off greater volumes of gas than normal, they can also tell them the type of gas it is. This gives people time to prepare for an eruption and is also useful as large quantities of some gases such as co2 can be very toxic to people and animals
Explain how tilt meters can predict a volcanic eruption
As magma pushes up inside a volcano the angle of the slope can become greater. Sometimes just before an eruption the sides may sink slightly. Tilt meters can measure those changes, alerting scientists to the possibility of an imminent eruption
Explain how geothermal imaging can predict a volcanic eruption
It can be used to monitor the movement of the magma in a volcano as it picks up on the heat from the magma. Geothermal imaging can show where the hottest areas of magma are and how close they are to the surface. If magma is nearing the surface, then there is more likelihood that an eruption will happen soon
Explain how GPS, Satellites and drones can predict a volcanic eruption
Magma pushing up inside the volcano can cause the crater of a volcano to expand. Some satellites and drones can be equipped with measuring tools and GPS that will observe those changes
Explain how seismographs can predict a volcanic eruption
Earth tremors are very common prior to a volcanic eruption. Earth tremors usually increase in number and strenght as an eruption approches. Seismographs can detected and measured these Earth tremors some warnings than an eruption is imminent.
How can individuals prepare for a volcanic eruption
- Every household should have an emergency kit that is fully stocked
- Create an evacuation plan for yourself and your family. Also have a plan for pets and livestock
- Practise the evacuation plan with everyone in your family
How can local and national governments prepare for a volcanic eruption
- Local authorities and governments should have evacuation procedures and emergency rest centres in place.
- Working with the relevant experts e.g. seismologists, volcanologists governments and local authorities should look at when and where to evacuate people to safety. Experts such as seismologists and volcanologists can advise on the areas that are most at risk and where people are likely to require evacuation. They can also suggest and map out safe evacuation routes.
- Governments and local authorities must work with the media to ensure that warnings are provided to allow people time to evacuate.
- The government should encourage people living in volcanic areas to download reliable apps that will alert them, if the volcano is showing signs of erupting or is erupting.
- Public announcement systems with sirens can be added to areas to alert people’s attention, they should be tested regular to ensure they are in good working order
- Governments and local authorities should also ensure that they have the accommodation, materials and trained personnel required to operate emergency rest centres for those who have been evacuated.
- Local and national governments should also provide information to the public about what to include in emergency kits, how to protect their homes from volcanic products such as ash, inform them where evacuation centres are located, they can also encourage households to have an evacuation plan and practise it regularly
What should be put in an emergency kit and why
- A battery powered radio so you can tune into news programmes to find out what is happening and if you need to evacuate
- Non-perishable food, as they have a long shelf life and do not need to be refrigerated. Ensure it does not need to be heated up as you might not have electricity. A manual tin opener
- Drinking water (enough to last each of your family members several days) because volcanic ash and lava can contaminate and disrupt drinking water supplies.
- Flashlight because ash can short-circuit power supplies and lava destroy electricity pylons bringing down wires and causing power-cuts
What strategies are adopted in response to a volcanic eruption
- Short term aid
1. bottled water - reservoirs may be blocked with lava or polluted with volcanic ash and sulphur
2. food - supermarkets are unlikely to be open as many have been damaged or the staff have had to evacuate too
3. shelter - peoples may have been evacuated from their homes as they might have lived in the evacuation zone, so they will require somewhere to stay
4. blankets and clothing - people will have evacuated their moes and might not have had time to collect items, it could be very cold
5. medical aid - people may have been injured in the rush to evacuate and people with conditions such as asthma may struggle to control those conditions - Rescue response from national and international emergency services
- Removal of ash from susceptible areas to prevent hazards such as buildings collapsing.Ash should be disposed in accordance with community plans and directions. Suitable sites for disposing ash are 1. Abandoned rock quarries 2. Household gardens and lawns, if ashfall is light. 3. Farm land
Long-term aid
1. rebuilding of schools, hospitals and housing as they could have been destroyed during a volcanic eruption
2. Repair of utilities such as water supply
3. Building of transport and communications infrastructure
