Tephra studies in New Zealand: an historical review.

The development of tephra studies in New Zealand may be divided into four main periods: Period 1, late 19th century to late 1920s; Period 2, late 1920s to early 1950s; Period 3, early 1950s to 1973; Period 4, 1973 to late 1980s. The important events and advances that characterise each of these periods, and their causes and influences, are described with reference to contemporary scientists and their publications. Period 1: determination by dendrochronology of first numerical age of a prehistorical eruptive (Burrell Lapilli); first isopach map (Tarawera Tephra). Period 2: first tephra mapping in central North Island (for soil survey). Period 3: first use of 14 C dating; establishment of late Quaternary tephrostratigraphic framework by 'hand over hand' mapping in central North Island and Taranaki; initial development of tephra 'fingerprinting' using laboratory methods; application of tephrochronology to many disciplines. Period 4: revision and refinement of proximal stratigraphy, particularly in central TVZ calderas and on Mayor Island; extension of tephra mapping to distal regions, on and offshore, and to older deposits; advances in tephra correlation and dating methods; new tephrochronological applications; revolutionary studies of pyroclastic deposits for determining nature and effects of eruptions (physical volcanology and petrology); renewed awareness of volcanic hazards associated with tephra eruptions. The advances relate to indigenous, external, and 'individualistic' factors. They generally parallelled overseas trends but in some topics preceded or lagged behind them. Tephra studies, or "tephrology", may be regarded as having "come of age" early in the 1980s, about 100 years after the first tephrostratigraphic studies in New Zealand