Far-reaching volcanic hazards include volcanic ash, volcanic gases, lahars and tsunami.
Volcanic ash characteristics and impacts:
- Over 90% of all volcanic eruptions produce volcanic ash. Volcanic ash consists of fragments of rock that become airborne during a volcanic eruption. The general term for all such material is ‘tephra’, with ‘ash’ constituting the material less than 2 mm in size.
- Ash is dispersed by prevailing winds away from the volcano. Ash particles can be carried hundreds or even thousands of kilometres away from the volcano, and can cover large areas of land with ashfalls.
- Very thick falls can cause structural damage to buildings (e.g. roof collapse) leading to casualties. Casualties may also be indirectly sustained, for example during ash clean-up operations or in traffic accidents.
- Ashfalls can also cause a public health hazard, with the short-term health effects of ash exposure typically being irritation of the eyes and upper airways and exacerbation of pre-existing asthma.
- Ashfalls can also disrupt critical infrastructure services (e.g. electricity and water supply, aviation and other transport routes), damage buildings, and damage or disrupt agricultural production and other economic activities.
- If the project is related to agriculture, consult local agricultural agencies for advice on managing impacts to agricultural production.
- Even relatively thin ashfalls of a few millimetres can cause significant societal impacts, through widespread damage, disruption and economic loss.
- Impacts can be long-lived, either because eruptions may be long-duration or because ashfalls may be remobilised by wind, water, traffic or human activities.
For further information on volcanic ash and its impacts, refer to the Volcanic Ash Impacts and Mitigation website hosted by the US Geological Survey: https://volcanoes.usgs.gov/volcanic_ash/
Specific impacts and mitigation advice for volcanic ashfall on buildings, facilities and critical infrastructure
- Thin ashfalls are generally disruptive rather than destructive, and many ash impacts can be successfully anticipated and mitigated against.
- Ash is extremely abrasive, and can cause severe damage to assets such as hydroelectric power generation turbines, pump impellers and bearings in motors. Take all possible steps to protect equipment such as closing water intakes and protectively shutting down pumps and motors, if possible.
- Cover and isolate vulnerable systems and equipment where possible, e.g. protect computers and electronics, exclude ash from buildings, cover exposed equipment, and plan to clean up ash promptly.
- Ash clean-up can be time-consuming and expensive. Pre-event planning can help save time and expense by considering personnel and equipment requirements, identification of potential disposal sites and strategies for stabilising ash deposits.
- Develop ash management plans, including provisions for clean-up and protocols to prevent ash ingress into buildings.
A series of posters providing impact and mitigation advice for critical infrastructure managers and operators are available at the following website hosted by GNS Science: http://www.gns.cri.nz/Home/Learning/Science-Topics/Volcanoes/Eruption-What-to-do/Ash-Impact-Posters
Consider the frequency and related possible consequences from volcanic ash hazards by reading these resources and learning about nearby and regional volcanoes. Plan measures based on the resources for rapid response if you consider that the chance of impact will be sufficiently disruptive.
- Volcanoes can emit volcanic gases not only during eruptions, but also between eruptions.
- Volcanic gases are dispersed downwind and may travel hundreds or even thousands of kilometres.
- The main gases emitted by volcanoes are water vapour, carbon dioxide and sulphur dioxide. Of these, sulphur dioxide (SO2) has the greatest consequences for people and infrastructure due to its ability to form sulphuric acid droplets.
- Acidic gases can cause health hazards, damage to crops, and accelerated corrosion damage to metal fittings and structures.
Volcanic gases: actions
- If possible, contact the local volcano observatory or geological hazards agency to determine whether volcanic gas hazards are present in the project area.
- Consult local agencies and community leaders to find out about gas hazards in the project area.
- If the project is related to agriculture, consult local agricultural agencies for advice on appropriate crop types that may be more resistant to the effects of acidic gases.
- Be aware that metal components and fittings may be subjected to accelerated corrosion. It may be possible to replace them with more resistant materials such as stainless steel.
Health and safety considerations
- Understand legal health and safety obligations to workers at the project and ensure that the project has appropriate procedures to meet these.
- These obligations vary between countries and organizations.
- Understand implications of working in environments where ash and/or gas hazards may be present:
- Common issues associated with ashfall include
- exposure to fine airborne ash
- slips and falls during ash cleanup operations, particularly from roofs and ladders
- strain injuries from moving heavy ash
- increased risk of traffic accidents due to loss of visibility and traction and coverage of road markings
- Acid-forming volcanic gases such as sulphur dioxide are irritating to eyes, throats and respiratory tract, with asthmatic individual being highly sensitive.
- Provide personal protective equipment for personnel working in hazardous environments.
For further, comprehensive information on volcanic health hazards and advice on dust and gas masks and personal protective equipment, see the website of the International Volcanic Health Hazard Network