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
What can you do?

A volcano is a vent or hole in the earth's crust, where hot melted rock or magma pushes up from inside the earth and can erupt in a huge explosion. Lava flows, rock, pumice, ash and gases can pour out and be very destructive. 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.

Mount Ruapehu

Ruapehu 1995

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.

Good information is available on our living earth - and a live camera in a volcano.

Gisborne 1995 – School girls cover up to protect themselves from ash in the air

Previous impacts in Hawke's Bay

As the nearest volcano is about 100 km away, Hawke's Bay is spared many of the multiple and highly damaging near-source effects of a volcanic eruption, except from massive eruptions from the Taupo Volcanic Centre. Instead, the region is vulnerable to volcanic ash-falls and their associated hazards, because the prevailing winds in the North Island are from the west and south.

Hawke's Bay peat bogs, swamps and road cuttings record a complex sequence of ash layers from Taupo, Okataina, Ruapehu and Taranaki volcanoes dating back over 20,000 years. From scientists understanding of New Zealand's volcanoes, eruptions from the Okataina and Taupo volcanic centres may produce sufficient volcanic ash to have significant impacts on Hawke's Bay, while large eruptions from Ruapehu, Tongariro, Ngauruhoe and Taranaki can have a lesser impact. More recently ash-falls from Ruapehu in 1945, 1975, 1995 and 1996 have affected the region; and Tongariro in 1896. Eruptions from White Island and other volcanoes are not likely to affect Hawke's Bay.

The expected return period for ash-fall thickness at coastal locations in Hawke's Bay, are shown below:

Ash Depth Return Period

Trace - 1mm 20 years

1 - 5mm 100 years

50 - 100mm 1000 years

^Top^

When cleaning up ash it is important to have protection for your eyes and breathing (Photo: GNS)

What can you do?

Have face masks available – large handkerchiefs or scarves are a reasonable substitute. Know how to disconnect any roof-fed water supply if required. Disconnection is only required when an ash fall warning has been given or ash begins to fall.

During an ash fall

Listen to the radio for advice and information
Stay indoors
Close windows and doors
Do not run air-conditioning or clothes dryers with outside connection
If outside, seek shelter; use a mask or handkerchief for breathing
Disconnect roof-fed water supplies before ash falls
Keep your car under-cover or cover it if possible
Do not drive unless you have to, but if you must drive, drive slowly as ashfall will reduce visibility
If you have driven in ashfall you will need to check your air-filter, change your cars oil and oil filter, and ensure ash has been removed from windscreen wipers.
Only pick up your children from school when requested. Schools will be notified of emergency procedures to be taken.
Keep pets indoors
If you are uncertain of what to do seek advice from Civil Defence

After an ash fall

Remove ash as soon as possible but remember ash particles commonly have sharp broken edges making it a very abrasive material.
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
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.
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/emergency-management/volcanoes/

^Top^