Volcano-sedimentary processes around New Zealand’s active andesite and rhyolite volcanoes

Date: 21 – 25 January 2026
Leader: Anke Zernack

Starting in New Plymouth, this field trip focuses on volcanic and sedimentary processes around New Zealand’s most prominent andesite stratovolcanoes, Mounts Taranaki, Ruapehu and Tongariro. We will explore the range of comprised lithofacies, including deposits produced by repeated edifice growth and collapse, and other landscape-shaping events recorded in the extensive volcaniclastic ring plains around these volcanic centres. Depositional processes, sedimentary characteristics and facies transitions will be discussed with respect to origin, transport and emplacement mechanisms, geomorphic setting and climate influences. We will also investigate the range of internal and external factors that control the nature of ring-plain accumulation and evolution of volcanic landscapes, including the impact of the 232CE rhyolitic Taupo eruption and its widespread products. This will be complemented by exposures of primary volcanic deposits that built the modern-day edifices to provide a holistic picture of the nature, frequency and magnitude of hazards from this type of volcano. Participants will gain a comprehensive understanding of stratovolcano growth and collapse processes, the spectrum of produced volcanic and sedimentary deposits and landscape features, visiting some of the best-exposed, most complete examples of volcaniclastic ring plain successions in the world. Apart from outstanding Geology and natural beauty, this trip also offers a taste of unique Kiwi outdoor experiences, including swimming at Taranaki’s beautiful black-sand beaches, white water rafting down the Tongariro River and a ride in the sky waka gondola at Mt. Ruapehu with spectacular views across the world-heritage-listed mountain area.

The Manganui gorge on the upper flanks of Mt. Taranaki provides excellent outcrops of the Holocene edifice stratigraphy, including lava flows, block-and-ash flow deposits and tephra layers.

Coastal cliffs of the Taranaki Peninsula display some of the best exposures of volcaniclastic lithofacies in the world, including spectacular cross-sections through volcanic debris-avalanche deposits derived from catastrophic edifice failure like the proximal facies of the Maitahi debris-avalanche deposit, which comprises large megaclasts that preserve the original edifice stratigraphy.

The long-lived Opunake river systems comprises an exceptional record of volcanic mass-flow and fluvial deposits from the last 20,000 years. Continuous aggradation, channel shifting and lateral migration resulted in a complicated network of overlapping channels, which cut into and eroded the underlying strata, often just preserving lenses of older deposits that formed in previous channels.

The Sky Waka Gondola travels through the rugged and breathtaking lava landscapes of the Whakapapa Ski Area on Mt Ruapehu up to 2,000 m asl, where riders are treated to panoramic views of the world heritage area around Mount Ngāuruhoe, Tongariro, and Ruapehu (phot from www.nationalpark.co.nz).

The widespread Taupō Ignimbrite was emplaced during the climactic phase of the 232 CE eruption of Taupo Volcano, which significantly altered the landscape of the central North Island and beyond, including the Tongariro/Ruapehu volcaniclastic ring plain.