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首页> 外文学位 >Explosive rhyodacitic volcanism: The evolution and frequency of pre-1883 eruptions at Krakatau volcano, Indonesia.
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Explosive rhyodacitic volcanism: The evolution and frequency of pre-1883 eruptions at Krakatau volcano, Indonesia.

机译：爆炸性的流纹岩火山作用：1883年以前印度尼西亚喀拉喀托火山的爆发演变和频率。

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摘要

Major explosive eruptions of Krakatau volcano, Indonesia, during the last 8,000 years have discharged crystal-poor calc-alkaline dacites and rhyodacites. The geochemistry and petrography of these rocks indicate that fractional crystallization of a basaltic parent produced these evolved magmas. Magma mixing is also an important process producing some of the evolved magmas. Pre-eruptive temperatures and possibly magma chamber depth have also varied between eruptive events.; Variations in magma composition, petrogenetic processes, and chamber conditions are attributed to a compositionally-stratified magma chamber, with a possible secondary, shallow chamber. Eruptions of homogeneous rhyodacite occur when a thick layer of rhyodacitic magma is present at the top of a stratified chamber. In contrast, eruptions of strongly mixed rhyodacite and andesite occur when the rhyodacite layer has been largely depleted in the main chamber or when andesitic magma intrudes a shallow chamber of rhyodacitic magma. Sequential tapping of a compositionally-zoned chamber may partially explain the proposed cyclic nature of Krakatau's eruptive behavior cited by previous workers.; The frequency of explosive eruptions at Krakatau was also investigated. Nine primary tephra layers have been identified in a sediment core recovered west of the Sunda Straits, Indonesia. Based on the mineralogy and compositions of glass shards, Krakatau volcano appears to be the source of six of the tephra layers. Toba caldera appears to be the source of one tephra layer, specifically the eruption which produced the Youngest Toba Tuff (YTT).; The presence of YTT ash in this core has several implications. Using this layer as a chronostratigraphic marker, the Krakatau tephra layers range in age from 4,000 to 127,000 years B.P., with an average recurrence interval of about 1 event per 21,000 years.; The occurrence of YTT ash in the Sunda Straits region also has implications for the size of the eruption and transport of material. The distribution of ash suggests the co-ignimbrite column injected ash into both hemispheres. The distribution may also have been affected by winds during the summer monsoon. Revised estimates of the size of the YTT are identical to previous estimates (2800 km3 DRE).
机译：在过去的8000年中，印度尼西亚Krakatau火山的主要爆炸事件释放了晶体贫乏的钙碱性dacites和rhydacites。这些岩石的地球化学和岩石学表明，玄武岩母体的部分结晶产生了这些演化的岩浆。岩浆混合也是产生一些演化岩浆的重要过程。喷发前的喷发前温度和可能的岩浆室深度也有所不同。岩浆成分，成岩过程和腔室条件的变化归因于成分分层的岩浆腔室，可能还有次级浅层腔室。当在分层室的顶部存在厚层的流纹​​岩岩浆时，会发生均质的流纹岩喷发。相反，当流纹岩层已在主室中大量耗尽时或当安山岩岩浆侵入到浅流纹岩岩浆室中时，就会发生强烈混合的流纹岩和安山岩的爆发。顺序敲击组成区域的腔室可能部分地解释了先前工作人员所引用的Krakatau喷发行为的拟议循环性质。还调查了喀拉喀托爆发爆炸的频率。在印度尼西亚the他海峡西侧发现的沉积岩心中发现了九个主要的特非拉层。根据矿物学和玻璃碎片的成分，喀拉喀托火山似乎是其中的六个特非拉层的来源。鸟羽破火山口似乎是一层特非拉的来源，特别是产生最年轻的鸟羽凝灰岩（YTT）的喷发。 YTT灰分在该岩心中的存在具有多种含义。用这一层作为年代地层标记，克拉卡图特菲拉层的年龄范围为公元前4,000至127,000年，平均复发间隔为每21,000年1次。在Sun他海峡地区，YTT灰分的发生也对物质的喷发和运输的规模产生了影响。灰分的分布表明共燃柱将灰分注入了两个半球。夏季季风期间，分布也可能受到风的影响。 YTT尺寸的修订估算值与以前的估算值相同（2800 km 3 DRE）。

著录项

  • 作者

    Beauregard, Jennifer Livesley.;

  • 作者单位

    University of Rhode Island.;

  • 授予单位 University of Rhode Island.;
  • 学科 Geology.; Geochemistry.
  • 学位 Ph.D.
  • 年度 2001
  • 页码 358 p.
  • 总页数 358
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 地质学;地质学;
  • 关键词

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