Volcano

GeoNet continuously monitors New Zealand's active volcanoes.

Gas sampling from a fumarole on White Island.

GeoNet and Volcanoes

New Zealand's active volcanoes include Raoul Island (Kermadecs), the Auckland Volcanic Field, the large caldera volcanoes of Taupo and Okataina, and the active cones of Taranaki/Egmont, Ruapehu, Tongariro-Ngauruhoe and White Island. Particular attention is paid to the frequently active volcanoes (Ruapehu, Tongariro-Ngauruhoe and White Island). Local, regional and central government authorities, plus the aviation and tourism industries, media and the public, need to know if there are any changes to the volcanoes' behaviour. The overall activity is quantified by setting an alert level from 0 to 5 for each volcano. Responding agencies in New Zealand are notified whenever the alert level changes, and they use it to determine the type and scope of their responses. Volcano alert bulletins are issued whenever there is a significant change in volcanic activity in New Zealand.

Four areas of science are commonly used in studying the behaviour of a volcano: geology, geophysics, geochemistry and geodesy. Data from all disciplines is collected, analysed, and cross-referenced, to help give an understanding of behaviour at the volcanoes and an insight to future eruptions.

Monitoring

Activities carried out by GeoNet include: 

• Visual observations: Volcanologists regularly visit the volcanoes to assess their status and collect data. Some volcanoes are also watched by cameras in order to provide a visual record of activity for correlation with other monitoring instruments.
• Seismic monitoring: Seismometers measure ground vibration, and these are used to locate any local volcanic earthquakes resulting from the subterranean movement of molten material or gases. The readings may also be used to determine the level of volcanic tremor, which can be caused by the movement of gas and steam or molten material through the volcano.
• Chemical analysis: The chemistry of gases emitted from steam vents and craters, and of water from crater lakes and thermal springs, is measured and used to detect any changes in volcano characteristics.
• Ground deformation: The movement of molten material beneath the surface of the earth can cause changes to the land above it. Repeated measurements using surveying techniques, and latterly GPS locations, are used to track changes. Close by volcanoes, tilting of the landscape can even be measured by the changing levels of lakes.