New Zealand's active volcanoes include Raoul Island (in the Kermadec Islands), 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 a Volcanic 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. Volcanic 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 are collected, analysed and cross-referenced, to help give an understanding of behaviour at the volcanoes and an insight to future eruptions.