气候变化领域集成服务门户(CCPortal): Complex crater fields formed by steam-driven eruptions: Lake Okaro, New Zealand

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DOI	10.1130/B35276.1
	Complex crater fields formed by steam-driven eruptions: Lake Okaro, New Zealand
	Montanaro C.; Cronin S.; Scheu B.; Kennedy B.; Scott B.
发表日期	2020
ISSN	167606
起始页码	1914
结束页码	1930
卷号	132 期号:2021-09-10
英文摘要	Steam-driven eruptions are caused by explosive vaporization of water within the pores and cracks of a host rock, mainly within geothermal or volcanic terrains. Ground or surface water can be heated and pressurized rapidly from below (phreatic explosions), or already hot and pressurized fluids in hydrothermal systems may decompress when host rocks or seals fail (hydrothermal eruptions). Deposit characteristics and crater morphology can be used in combination with knowledge of host-rock lithology to reconstruct the locus, dynamics, and possible triggers of these events. We investigated a complex field of >30 craters formed over three separate episodes of steam-driven eruptions at Lake Okaro within the Taupo volcanic zone, New Zealand. Fresh unaltered rock excavated from initially >70 m depths in the base of phase I breccia deposits showed that eruptions were deep, "bottom-up" explosions formed in the absence of a preexisting hydrothermal system. These phreatic explosions were likely triggered by sudden rise of magmatic fluids/gas to heat groundwater within an ignimbrite 70 m below the surface. Excavation of a linear set of craters and associated fracture development, along with continued heat input, caused posteruptive establishment of a large hydrothermal system within shallow, weakly compacted, and unconsolidated deposits, including the phase I breccia. After enough time for extensive hydrothermal alteration, erosion, and external sediment influx into the area, phase II occurred, possibly triggered by an earthquake or hydrological disruption to a geothermal system. Phase II produced a second network of craters into weakly compacted, altered, and pumice-rich tuff, as well as within deposits from phase I. Phase II breccias display vertical variation in lithology that reflects top-down excavation from shallow levels (10-20 m) to >70 m. After another hiatus, lake levels rose. Phase III hydrothermal explosions were later triggered by a sudden lake-level drop, excavating into deposits from previous eruptions. This case shows that once a hydrothermal system is established, repeated highly hazardous hydrothermal eruptions may follow that are as large as initial phreatic events. © 2019 Geological Society of America.
语种	英语
来源期刊	Bulletin of the Geological Society of America
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/184737
作者单位	Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München, Theresienstrasse 41, Munich, 80333, Germany; School of Environment, University of Auckland, Science Centre, Building 302, 23 Symonds Street, Auckland Central, 1010, New Zealand; Department of Earth Sciences, University of Canterbury, Private Bag 4800, Christchurch, 8140, New Zealand; GNS Science, 114 Karetoto Road, Wairakei, 3377, New Zealand
推荐引用方式 GB/T 7714	Montanaro C.,Cronin S.,Scheu B.,et al. Complex crater fields formed by steam-driven eruptions: Lake Okaro, New Zealand[J],2020,132(2021-09-10).
APA	Montanaro C.,Cronin S.,Scheu B.,Kennedy B.,&Scott B..(2020).Complex crater fields formed by steam-driven eruptions: Lake Okaro, New Zealand.Bulletin of the Geological Society of America,132(2021-09-10).
MLA	Montanaro C.,et al."Complex crater fields formed by steam-driven eruptions: Lake Okaro, New Zealand".Bulletin of the Geological Society of America 132.2021-09-10(2020).