Some Studies of New Zealand Quaternary Pyroclastic Rocks

The development of volcanic "ash" studies in New Zealand can be traced through three broad periods (Jeune 1970). During the late 19th century the extensive pumice deposits surrounding Lake Taupo received considerable comment (Crawford 1875, Smith 1876 and Cussen 1887). Thomas (1887) recognised a covering of younger andesitic ash from Mts. Tongariro and Ruapehu overlying the pumice from Taupo and in his 1888 report on the eruption of Mt. Tarawera in 1886, Thomas provided a valuable description of the eruption and the deposits resulting from it. Tephra deposits received only cursory attention during the following years until soil surveys initiated as part of the research effort into bush sickness demonstrated a relationship between incidence of the disease and soil derived from tephra (Aston 1926). Extended soil surveys followed (Granger 1929, 1931, 1937, Taylor 1930, 1933, Grange and Taylor 1931, 1932) during the course of which many important soil forming tephras were named, described and mapped. On the basis of minerals studies, contributions were recognised from four recently active volcanic centres; Taupo, Rotorua, Tongariro National Park and Mt. Egmont.