SURVEILLANCE OF WHITE ISLAND VOLCANO, 1968–1972

Abstract

A new sub-crater developed during explosive eruption of White Island in July 1971. The precise level net installed on the main crater floor in 1967 was enlarged in 1969 and afterwards relevelled five times prior to the 1971 eruption and three times following it. Signs of bulging of the crater floor, believed to represent buildup of pressure, were noted prior to and following the 1971 eruption. The crater-floor deformation is discussed in relation to measured temperature and magnetic changes, and the conclusion reached that small eruptions of White Island are probably caused by explosive clearing of blocked conduits.