Leaders: Adrian Pittari, Marlena Prentice, Elham Yousefzadeh

Duration: 3 days (2 nights)

Level of fitness: The majority of this field trip involves stops close to the bus or easy walks within half to one hour of the bus.  Most short walks will be on well-formed tracks. The Wairere Falls track is an exception being a two-hour round trip requiring moderate fitness.

Summary: Ignimbrite plateaux and their underlying volcanic successions are a prominent feature of the central North Island (New Zealand) volcanic environment. This field trip will examine various landscape-forming outflow ignimbrites of the Waikato region to the west of Rotorua over the last four million years.  Geologist Patrick Marshall in the 1920s first classified these enigmatic North Island deposits, correctly recognised their pyroclastic origin and thus coined the term ‘ignimbrite’. We will highlight how various eruption, emplacement and post-emplacement processes of large pyroclastic flows lead to the diversity of compositions, textures and landform patterns associated with their deposits.  The ignimbrites we plan to visit include those described by Marshall.  We will visit the large-volume, crystal-rich Waiteariki, Ongatiti and Whakamaru ignimbrites that were end-member supereruptions of the early Taupo Volcanic Zone and contrast these with more typical crystal-poor ignimbrites. Applications to groundwater quality, hydroelectric dam construction and the extraction of dimension stone will also be discussed. Sometimes they form spectacular waterfalls; in more subdued landscapes of rolling hills and bluffs they were the ideal home for the hobbits of the Shire!