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DOI	10.1016/j.earscirev.2021.103697
	Classification of ignimbrites and their eruptions
	Giordano G.; Cas R.A.F.
发表日期	2021
ISSN	00128252
卷号	220
英文摘要	The term “ignimbrite” probably encompasses the one of the largest ranges of deposit types on Earth, associated with the partial to total collapse of explosive eruption columns feeding pyroclastic density currents. Surprisingly, there is no quantified classification scheme for ignimbrite types, as there is for fallout deposits, and this is a remarkable deficiency of modern volcanology. This has so far prevented the identification of standardized descriptors for ignimbrites and the improvement of methods for the documentation of their characteristics, such as happened for fallout deposits, building on the classification scheme proposed by Walker in 1973. Despite some earlier attempts, ignimbrite types do not conform to eruption style nomenclature. In this paper, we explore and discuss descriptors for a classification scheme based on the correlation of runout, areal extent, aspect ratio and volume from a compiled database comprising 92 ignimbrites, which then allows current understanding of pyroclastic flow dynamics to be considered. We refer to single ignimbrite outflow units, i.e. emplaced without significant breaks in their sedimentation, in extra-caldera settings and forming individual cooling units, irrespective of internal lithofacies architecture. Our main finding is that ignimbrites show remarkable power-law relationship between dispersal area/equivalent runout and bulk volume. Runout is directly related to increasing mass flow rate feeding the pyroclastic current. Volume is related to the magnitude of the flow event. We therefore propose that by measuring first order field observables such as bulk volume and dispersal area provides the opportunity to evaluate magnitude and intensity of related pyroclastic currents and, for large eruptions dominated by ignimbrites, of the eruption. Based on the relationships identified we propose that ignimbrites that originated from the collapse of single point-source eruption columns, usually smaller than 1 km3, are named “Vulcanian ignimbrites” and “Plinian ignimbrites” depending on the style of the eruption they are associated with. Larger ignimbrites that originated from caldera-forming eruptions along ring-fault fissure vents should be regarded as related to a separate eruption style - with respect to the common Hawaiian-Plinian trend -, where the effect of increased mass flow rate due to ring-fissure vents is dominant and controls the dynamics of the resulting collapsing fountains and pyroclastic flows, irrespective of the kind of eruption style that preceded the onset of the caldera collapse. These are named “caldera-forming ignimbrites” and are further subdivided into small, intermediate, large and super, based on their increasing erupted volume. © 2021 Elsevier B.V.
关键词	Caldera Classification Ignimbrites Mass flow rate Pyroclastic currents
英文关键词	caldera; classification; flow field; ignimbrite; lithofacies; plinian eruption; pyroclastic deposit; pyroclastic flow; volcanic eruption; volcanology; Hawaii [(ISL) Hawaiian Islands]; Hawaii [United States]; Hawaiian Islands
语种	英语
来源期刊	Earth Science Reviews
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/204033
作者单位	Dipartimento di Scienze – Sezione Geologia, Università di Roma Tre, Roma, Italy; Istituto di Geologia Ambientale e Geoingegneria, CNR, Montelibretti, 00010, Italy; School of Earth, Atmosphere and Environment, Monash UniversityVictoria, Australia; CODES and Earth Science, School of Natural Sciences, University of Tasmania, Australia
推荐引用方式 GB/T 7714	Giordano G.,Cas R.A.F.. Classification of ignimbrites and their eruptions[J],2021,220.
APA	Giordano G.,&Cas R.A.F..(2021).Classification of ignimbrites and their eruptions.Earth Science Reviews,220.
MLA	Giordano G.,et al."Classification of ignimbrites and their eruptions".Earth Science Reviews 220(2021).