Ground deformation patterns at White Island volcano (New Zealand) between 1967 and 2008 deduced from levelling data

Since 1967, levelling measurements have been conducted in the main crater of White Island volcano. Interpretation of these data using numerical modelling reveals that shallow pressure sources (200–600 m deep) extending up to the subsurface dominated the long-term deformation pattern consisting of inflation/deflation cycles. The time sequence of height changes, magnetic changes, and fumarole temperature and chemistry reveal that surface changes were caused by increasing temperature below the main crater, reflecting the presence of magma at shallow depth. The uplift and subsidence are interpreted in terms of increase or decrease in fluid pore pressure in response to changes of the heat and gas flux. The subsidence during and following eruptions could be also linked with removal of material at depth to feed the eruptions.