Volcanoes

Although there are no volcanoes in Hawke's Bay, the area has been affected by over 20,000 years of volcanic activity, mainly in the form of ash falls.

On this page

• Previous impacts in Hawke's Bay
• Expected return period for ash-fall thickness
• Volcanic Alerts
• What can you do?

A volcano is a landform that results from magma (molten rock within the earth) erupting at the surface. The size and shape of a volcano reflect how often it erupts, the size and type of eruptions, and the composition of the magma it produces. When pressure from gases within the molten rock becomes too great, gases drive the molten rock to the surface and an eruption occurs.  Lava flows, rock, pumice, ash and gases can pour out and be very destructive.  When the eruptions are too massive, the volcano collapses and forms a caldera, like Taupo which is now filled with lake water after one of the largest volcanic explosions ever known about 1800 years ago.  A volcano can be a small mountain, like in Auckland, or a large mountain like Ruapehu which was formed by lava from many thousands of eruptions and are still active today.   

In historic times, ashfalls from Ruapehu have affected the region in 1945, 1975, 1995 and 1996; and from Tongariro in 1896.  Peat bogs and swamps record a complex sequence of older ash layers from Taupo, Okataina, Ruapehu and Taranaki volcanoes dating back over 20,000 years. From our understanding of New Zealand's volcanoes, we can conclude that eruptions from the Okataina and Taupo volcanic centres may produce sufficient volcanic ash to have significant impacts on Hawke's Bay.  Large eruptions from Ruapehu, Tongariro, Ngauruhoe and Taranaki  may also produce enough ash to impact on the region but will have a lesser impact. Eruptions from White Island and other volcanoes are not likely to affect Hawke's Bay.
 
The return periods for ash-fall events are shown below:

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What can you do?

If you are at risk from volcanic activity, you should add to your emergency survival items the following:

• Dust masks and eye protection (see IVHHN Recommended Masks document at www.ivhhn.org 
• Plastic wrap (to keep ash out of electronics)
• Cleaning supplies such as a broom, vaccum cleaner with spare bags and filters, and a shovel.
• Consider that you could be stuck in your vehicle, so store emergency supplies in your vehicle too.

Also learn how to disconnect drainpipes/downspouts from gutters to stop drains clogging and to allow ash and water to empty from gutters onto the ground.  If you use a rainwater collection system for your water supply, disconnect the tank prior to ash falling.

During an ash fall

• Listen to the radio for civil defence advice and follow instructions
• If outside at the time of the eruption, seek shelter in a car or building.  If caught in volcanic ashfalls, wear a dust mask or use a handkerchief or cloth over your nose and mouth for breathing.
• Stay indoors as volcanic ash is a health hazard, especially if you have respiratory difficulties such as asthma or bronchitis. 
• When indoors, close all windows and doors to limit the entry of volcanic ash.  Place damp towels at thresholds.
• Do not run air-conditioning or clothes dryers with outside connection.
• Do not use phone lines with non-emergency calls. 
• If you have to go outside use protective gear such as masks and goggles and keep as much of your skin covered as possible.  Wear eyeglasses, not contact lenses as these can cause corneal abrasions.
• Stay out of designated restricted zones.
• Keep your car under-cover or cover it if possible
• Avoid driving in heavy ashfall.  Driving will stir up volcanic ash that can clog engines and stall vehicles.  Abrasion can damage moving parts, including bearings, brakes and transmissions.  If you have driven in ashfall you will need to check your air-filter, change oil and oil filters, and ensure ash has been removed from windscreen wipers, etc.
• Keep animals indoors where possible.
• If you are uncertain of what to do seek advice from Civil Defence

After an ash fall

• Listen to your local radio station for civil defence advice and follow instuctions.
• Stay indoors and away from volcanic ashfall areas as much as possible.
• When it is safe to go outside, remove ash as soon as possible but remember the fine, glassy pieces of volcanic ash can increase the health risks for children and people with respiratory conditions such as asthma, chronic bronchitis or emphysema.  
• Remember ash can be very abrasive.  Clean house roofs first to reduce windblown ash covering cleaned areas, repair damage to guttering and blocked down-pipes. 
• Do not over-water or soak the ash as it will form a glue-like material (not easy to remove) and add weight to the roof.  The best method is to lightly damp the ash (to prevent it billowing) and to sweep it up.
• Dampen and sweep ash from paths, driveways, and gutters.  Use water sparingly as the widespread use of water for clean-up may deplete public water supplies for drinking.
• Do not dump ash in the storm-water or sewage system as it will set firmly and cause future problems and flooding on your property - contact your council for information on the disposal of ash.
• Place ash in rubbish bags if possible and seal them.  Seek advice from your local Council on the disposal of ash in your community as ash is normally seperated from normal rubbish collection.
• Prevent further ash entering your house by restricting access to the most protected entrance.
• Vacuum indoor surfaces were possible or use a damp cloth to remove ash. Avoid vigorous rubbing.

Attached are two brochures published by the Cities and Volcanoes Commission 'The Health Hazards of Volcanic Ash - A guide for the public', and Guidelines on Preparedness before, during and after an ashfall'. You can find these and more information on their web site http://cav.volcano.info

Volcanic ash falls will also impact agriculture and forestry in Hawke's Bay.  The 'Volcanic Alert Brochure' produced by MAF outlines some strategies farmers could take to protect their livestock and farms.  Refer also the MAF Ash Impact Report on their website  http://www.maf.govt.nz/mafnet/rural-nz/adverse-events/volcanoes/volcano-eruption-impact/httoc.htm

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