VOLCANIC HAZARDS Flashcards
The nature and cause of volcanic hazards is …..
The distribution of volcanic hazards is ……
The magnitude and frequency of volcanic hazards are ….
Primary effects of volcanic hazards are ….
- Tephra - all material ejected into the atmosphere (Eyjafjallajokul, Iceland)
- Pyroclastic flow - very hot, high velocity flows made up of tephra and gas (Mt Vesuvius )
- Lava flow - often unstoppable but slow, causes secondary effects like fire (Nyiragongo)
- Volcanic gases - include carbon dioxide, carbon monoxide, hydrogen sulphide, sulphur dioxide and chlorine
Secondary effects of volcanic hazards are …….
1 - Lahars – fast moving mudflows made up of ash and water (Nevada del Ruiz, Colombia in 1985 destroyed the town Amero and killed ¾ of the population)
- Flooding – eruption cases the melting of glaciers and ice caps (Eyjafjallajökull, Iceland)
- Volcanic landslides – they have high velocity and momentum = can cross between valleys (Mt St Helens in 1980 had a volume of 2.5km3 and went of a 400m high ridge 5km from the volcano
- Tsunamis – sea wave generated by violent eruptions (Tonga in Jan 2022, flooded the middle of the island)
- Acid rain – eruptions release gases including sulphur which combines with atmospheric moisture and forms acid rain
- Climatic change – the ejection of huge amounts of volcanic debris into the atmosphere can reduce global
Environmental effects of volcanic hazards …..
- ash clouds block the sun = volcanic winter
- destroys crops/plants + kills animals
- makes soil more fertile
- change water quality
Political effects of volcanic hazards ….
- government buildings damaged + its contents
Social effects of volcanic hazards …..
- houses destroyed
- death / injury
- forced to move away from home / evacuate
- infrastructure damaged
- food shortages
Economic effects of volcanic hazards ……
- damages economy as eg, crops get destroyed
- money needed to rebuild
- infrastructure damaged - roads
- tourism increase
Responses to volcanic hazards ?
Monitoring, prediction, protection
- when looking at the volcano you analyse the geological factors and its past eruptive history
monitoring instruments include:
- Satellites: use cameras to see if there is any
deformations in the shape of the volcano - Seismographs: measure movement in the earth’s crust. An earthquake might lead to an eruption
- Tiltmeters: a container of liquid that shows how much the ground moves which could be a precursor to volcanic activity – magma movements can cause bulges/hollows in the ground
- Hydrology instruments: pressure sensors, water detectors, maps. Monitoring water changes can provide info about volcanic activity – sudden change could predict an eruption
- Gas trapping bottles: as magma moves towards the surface, the pressure releases gas, if more gas is collected, there’s more magma rising to the surface = more likely to be an eruption
Protection – preparing for the event
- Use monitoring to find what time the area should be evacuated
- governments of several countries with volcanos such as New Zealand have made risk assessments and from them produced series of alert levels to warn the public of the threat
- also use geological studies of the nature and extent of former eruptions to find areas at greatest risk
- it’s possible to divert lava away from build environments. E.g. on Mt Etna, they dug trenches, dropped blocks and used lava to slow and divert the flow. Also in parts of Hawaiian Islands barriers have been built across valley to protect settlements from lava flows and lahars
Name of lower HDI country volcanic case study?
Mt Nyiragongo, Congo
Mt Nyiragongo, Congo Facts:
- characteristics of place
- characteristics of hazard
- primary / secondary effects
- risks / vulnerabilities
- long / short term management
Characteristics of place
- dense urban population in Goma
- 228th poorest country in the world
- still recovering from civil war, where over 5 million people died
- rapid growth of informal housing in Goma (from rural urban migration)
Characteristic of hazards
- constructive boundary
- large balsaltic stratovolcano
- VEI 1
- fast moving lava (42kmph)
Primary effects
- lava destroyed villages
- 147 died (47 in first 24hrs)
- 400,000 fled to Rwanda
- 16,000 homes destroyed
Secondary effects
- lava ignited fires across Goma
- 350,000 depended on aid
- drinking water poisoned
Risks
- since 1882, there have been 34 eruptions
- large agricultural region (dense pop)
Vulnerable
- warning was not communicated
- Rwanda struggled to provide food
- fast flowing lava -> could not be outrun
Long Term Management
- planning: retraining of officials with precise evacuation plans.
- preparation: 30 new signs that detail early warning signs and evacuation routes in high risk areas. Evacuation drills in communities
- prediction - observatory for volcano. Lava lake is visible from the air so can be monitored
Short Term Management
- intternational aid sent by air got disrupted by damaged airport in Goma
- $35 million in aid
- refugee camps set up
- NGOs provided chlorinated water to prevent spread of Cholera
Name of higher HDI volcanic case study?
Eyjafjakkajoukull, Iceland
Eyjafjnallajokull, Iceland Facts:
- characteristics of place
- characteristics of hazard
- primary / secondary effects
- risks / vulnerabilities
- long / short term management
Characteristics of place?
- 28th richest country
- nobody lives below poverty line
- rural areas , sparsely populated
Characteristics of hazard ?
- VEI 4
- constructive boundary
- glacial covered stratovolcano
- interaction between lava and ice created ash
- eruption lasted one month
Primary effects
- 0 deaths
- 700 evacuated (strong reason for no loss of life )
Secondary effects
- ash cloud stopped 100,000 jet engines in Europe. Airline lost £130million per day
- water supplies contaminated from ash
- surrounding rivers were silted with ash
Risk:
Low as people are educated on what to do eg, board up windows and bring in livestock
Vulnerable:
- high wealth, meant vulnerability was low as could afford to evacuate people.
Long term response:
- investment into prediction of the flight of ash clouds (decrease vulnerability in the future)
Icelandic government rebuilt riverbanks higher than before - flash floods
- getting people back into homes
Short Term Response:
- 700 people evacuated
- livestock taken in to escape ash
- 6 day ban on flights and exclusion zone created
Compare case studies ……..
