@article{oai:niigata-u.repo.nii.ac.jp:00027983,
 author = {片岡, 香子 and Manville, Vern},
 journal = {新潟大学積雪地域災害研究センター研究年報, 新潟大学積雪地域災害研究センター研究年報},
 month = {Dec},
 note = {Volcanic activities provide cataclysmic hazards to surrounding environments and human life by various eruptive and hydrologic processes, e.g., lava flows, pyroclastic flows, pyroclastic fallout, debris avalanches, debris flows, and flood flows. Although there are many studies dealing with the prevention and mitigation of volcanic hazards, these are mostly concentrated on primary eruptive processes occurring in areas proximal to active volcanoes. However, studies from historic and pre-historic eruptions have shown that the remobilization and resedimentation of volcanic debris in the aftermath of an eruption will potentially generate severe hazards in far-distant downstream areas, especially when a large-scale rhyolitic eruption triggers the remobilisation. This paper introduces the research on volcaniclastic remobilisation and resedimentation in the aftermath the 1.8 ka Taupo eruption, Northern Island, New Zealand that have been addressed mainly by groups from the Institute of Geological and Nuclear Sciences and the Department of Geology at the University of Otago, New Zealand. Spatiotemporal variations in volcaniclastic remobilisation and resedimentation occur along the Waikato River in response to the 1.8 ka Taupo large-scale explosive eruption. During the eruption, climactic emplacement of the Taupo ignimbrite (30km^3) caused the destruction of drainage networks and modification of pre-existed topography over an area of 20,000 km^2. This resulted in drastic depositional system changes not only in proximal areas directly affected by ignimbrite deposition but also in far downstream areas, beyond the limit of ignimbrite emplacement, by inundation with large volumes of reworked voIcaniclastic debris. The example from the aftermath of the 1.8 ka Taupo eruption shows two significant points in terms of volcanic hazards. Firstly, the hydrological remobilization of volcaniclastic material and its impact may constitute severe hazards more widespread and persistent than the primary eruptive impacts. Although people living far from volcanoes are usually prone to ignore volcanic hazards because they are less affected by primary volcanic ejecta, they may be vulnerable to the impacts of remobilization and resedimentation of volcaniclastic debris on such distant areas. Secondly, for rhyolitic caldera volcanoes associated with emplacement of a large-ignimbrite, the delivery pattern of volcanic sediment load through river drainages does not match with that of cone type stratovolcanoes, for which models are available. The nature and distribution of ignimbrite relative to topography and drainage patterns enhances the formation of ephemeral and intra-caldera lakes that can impound large amounts of water after the eruption. Such impoundments can potentially cause catastrophic outbursts and floods and complicate predictions of the timing and scale of remobiIisation in the aftermath of the eruption. Thus, volcaniclastic resedimentation by various hydrologic processes can create more serious hazards than actual volcanic eruptions, in terms of variety, persistence, extensiveness, and sudden onset. Hence, studies on the sedimentological features of voIcaniclastic material should be enhanced for further understanding, prevention, and mitigation of post-eruptive volcanic hazards by voIcaniclastic remobilization and resedimentation.},
 pages = {77--89},
 title = {火山砕屑物質の再動・再堆積作用と火山災害 : ニュージーランド北島, タウポ噴火 (1800年前) の例},
 volume = {24},
 year = {2002}
}