The Taurewa Eruptive Episode: evidence for climactic eruptions at Ruapehu volcano, New Zealand |
| |
Authors: | Susan L Donoghue Alan S Palmer Elizabeth McClelland Kate Hobson Robert B Stewart Vincent E Neall Jèrôme Lecointre Richard Price |
| |
Institution: | (1) Department of Earth Sciences, University of Hong Kong, Pokfulam Road, Hong Kong e-mail: donoghue@hkucca.hku.hk, Fax: +852-25176912, HK;(2) Institute of Natural Resources, College of Science, Massey University, Private Bag 11-222 Palmerston North, New Zealand, NZ;(3) Department of Earth Sciences, University of Oxford, Parks Road, Oxford, OX1 3PR, UK, GB;(4) School of Earth Science, La Trobe University, AUS-3083 Bundoora, Australia, AU |
| |
Abstract: | The ca. 10,500 years B.P. eruptions at Ruapehu volcano deposited 0.2–0.3 km3 of tephra on the flanks of Ruapehu and the surrounding ring plain and generated the only known pyroclastic flows from this
volcano in the late Quaternary. Evidence of the eruptions is recorded in the stratigraphy of the volcanic ring plain and cone,
where pyroclastic flow deposits and several lithologically similar tephra deposits are identified. These deposits are grouped
into the newly defined Taurewa Formation and two members, Okupata Member (tephra-fall deposits) and Pourahu Member (pyroclastic
flow deposits). These eruptions identify a brief (<ca. 2000-year) but explosive period of volcanism at Ruapehu, which we define
as the Taurewa Eruptive Episode. This Episode represents the largest event within Ruapehu's ca. 22,500-year eruptive history
and also marks its culmination in activity ca. 10,000 years B.P. Following this episode, Ruapehu volcano entered a ca. 8000-year
period of relative quiescence. We propose that the episode began with the eruption of small-volume pyroclastic flows triggered
by a magma-mingling event. Flows from this event travelled down valleys east and west of Ruapehu onto the upper volcanic ring
plain, where their distal remnants are preserved. The genesis of these deposits is inferred from the remanent magnetisation
of pumice and lithic clasts. We envisage contemporaneous eruption and emplacement of distal pumice-rich tephras and proximal
welded tuff deposits. The potential for generation of pyroclastic flows during plinian eruptions at Ruapehu has not been previously
considered in hazard assessments at this volcano. Recognition of these events in the volcanological record is thus an important
new factor in future risk assessments and mitigation of volcanic risk at Tongariro Volcanic Centre.
Received: 5 July 1998 / Accepted: 12 March 1999 |
| |
Keywords: | Ruapehu volcano Taurewa Formation Tephra Pyroclastic flow Remanent magnetism Taurewa eruptive episode Volcanic hazard |
本文献已被 SpringerLink 等数据库收录! |
|