Volcanic activity threatens people and property. The Waikato region has many volcanic centres that vary in activity and risk.
The central North Island features many landforms that have been created over the last 1.6 million years through volcanic activity (‘volcanism’). Volcanic soils are important in supporting farming and forestry.
Volcanism is the biggest source of death from natural disasters in New Zealand over the last 150 years. Over 100 people died when Mount Tarawera erupted in 1886, and 151 people were killed after a mudflow (‘lahar’) derailed their train at Tangiwai following Mount Ruapehu’s eruption in 1953. We need to monitor volcanic zones in our region to prepare for and minimise any effects from future volcanic activity.
Most of New Zealand’s volcanic activity has taken place in the Taupo Volcanic Zone (TVZ), a long rectangular area from White Island to Ruapehu.
Volcanic centres in the Waikato region include:
Ruapehu, Ngauruhoe and White Island are considered very active compared with other volcanoes around the world. The Taupo Volcanic Zone also includes the two most explosive caldera volcanoes, Taupo and Okataina.
Lake Taupo was formed by a series of eruptions, the most recent - around 1800 years ago - blasted out about 60 cubic kilometres of earth, rock and mud, leaving a massive crater. Lake Taupo:
Other volcanic centres such as Auckland and White Island are close to our region and could also affect people and property in the Waikato.
Volcanic hazards include ashfall, lava flows, lahars (mudflows) and pyroclastic flows.
As well as potentially threatening lives and property, any of these hazards may also damage our region’s:
The Institute of Geological and Nuclear Sciences has more information about what to do(external link) in the event of a volcanic eruption.
Ash is made up of small particles of exploded volcanic glass (less than 2 mm in size), which erupt from a volcano. Clouds of ash are carried by the wind, with the ash plume from a volcano often reaching high up into the atmosphere and showing up on satellite images.
Ashfall effects include:
Use our map to find out about volcanic ashfall zones in the Waikato region.
A lahar is a fast moving mixture of water and volcanic material which travels down the slopes of a volcano, concentrating in valleys and riverbeds. Lahars can also carry larger material within their flows as debris is ripped from the valley floor. Lahars are created when:
Mount Ruapehu has a crater lake and is particularly vulnerable to lahars. This was the cause of the Tangiwai disaster in 1953. Warning systems are currently being installed and various authorities and agencies are drafting contingency plans to ensure a co-ordinated approach when the next lahar occurs.
Lava flow rates can vary from 0.5 to 5,000 cubic metres per second (depending on the type of magma) but generally lava flows seen in New Zealand are slow moving. Magma is made up of molten material including rock, crystals and liquid that forms beneath the upper mantle or crust of the Earth. A black crust forms where the surface of the lava flow comes into contact with cooling air. This crust thickens and hardens into volcanic rock once the lava has cooled completely.
Most deaths resulting from lava flows are from burns. Some countries have had limited success with diverting lava flows by cooling them with seawater in an attempt to protect people and property.
Pyroclastic flows occur when an eruption plume collapses or is directed at ground level. This type of flow (made up of gases, molten glass and rock fragments) has a number of destructive effects:
Lake Taupo (essentially a huge crater lake) is our region’s most likely source of a pyroclastic flow should an eruption happen from beneath the Lake. Such an event would totally destroy the Taupo township and surrounding areas, as well as causing significant damage to the central North Island’s heavily forested areas.
The Institute of Geological and Nuclear Sciences (GNS) regularly monitors Lake Taupo as part of its volcano surveillance programme. Their studies show that Taupo has erupted 28 times during the past 26,500 years, with its last eruption 1800 years ago. Intervals between eruptions vary. At one stage a period of 3,000 years went by with no eruption, followed by two in 500 years.
The Institute of Geological and Nuclear Sciences(external link) (GNS) monitors and assesses New Zealand’s volcanoes regularly and issues scientific alerts. Alert levels give an indication of how active a volcano is, on a scale of 0-5. Normal background levels are ‘0’, while ‘5’ indicates a large volcanic eruption is in progress. Scientists look for changes in:
Changes in the above do not necessarily mean an eruption will happen. However, they are good indicators that something might happen. Find out more about what alert levels(external link) mean.
There are five volcano-seismic monitoring networks around New Zealand’s volcanoes - three of these are within the Taupo Volcanic Zone. Regular ground deformation surveys and water sampling are carried out on the Ruapehu Crater Lake. Geochemical surveys (such as sampling volcanic gases) are done on Mount Tongariro and the summit crater of Ngauruhoe.
Under the Resource Management Act 1991(external link) and the Civil Defence Emergency Management Act 2002, (external link)Waikato Regional Council has responsibilities in:
We've also been:
For policy information on natural hazards, see our Regional Policy Statement.(external link)