...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Journal of Volcanology and Geothermal Research >Glacial influence on caldera-forming eruptions
【24h】

Glacial influence on caldera-forming eruptions

机译：冰川对火山口形成爆发的影响

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

It has been suggested that deglaciations have influenced volcanism in several areas around the world increasing productivity of mantle melting and eruptions from crustal magma chambers. However, the connection between glaciations and increased volcanism is not straightforward. Investigation of Ar-Ar, U-Pb, andC~(14) ages of caldera-forming eruptions for the past million years in the glaciated arc of Kamchatka has lead to the observation that the majority of large-volume ignimbrites, which are associated with the morphologically preserved calderas, correspond in time with "maximum glacial" conditions for the past several glacial cycles. In the field, the main proof is related to the fact that glaciated multi-caldera volcanoes hosted thick glacial ice caps. Additional evidence comes from clustering Kamchatka-derived marine ash layers with glacial moraines in DSDP cores. Here we present a set of new results from numerical modelling using the Finite Element Method that investigate how the glacial load dynamic may affect the conditions for ring-fault formation in such glaciated multi-caldera volcanoes. Different scenarios were simulated by varying: (1) the thickness and asymmetric distribution of the existing ice cap, (2) the depth and size of the magmatic reservoir responsible for the subsequent collapse event, (3) the thickness and mechanical properties of the roof rock due to the alteration by hydrothermal fluids, (4) the existence of a deeper and wider magmatic reservoir and (5) possible gravitational failure triggered, in part, by subglacial rock mass build up and hydrothermal alteration. The results obtained indicate that: (1) Any ice cap plays against ring fault formation; (2) Asymmetric distribution of ice may favour the initiation of trap-door type collapse calderas; (3) Glacial erosion of part of volcanic edifice or interglacial edifice failure may facilitate subsequent ring fault formation; (4) hydrothermal system under an ice cap may lead to a quite effective hydrothermal rotting of the intracaldera roof rocks and hence to variations of their mechanical properties and inhibit/deflect ring fracture propagation; and (5) rock surface topography/load influenced by glacial erosion and ice volume change during the interstadials. Although, the analysis of the stress field may inform us about the possibility of ring-fracture initiation, it does not ensure its complete propagation. Parameters controlling this phenomenon are also discussed here. Overall, the maximal glacial time represent the most dynamic time in a multi-caldera volcano life (as compared to more quiet interglacial) promoting physical and chemical feedbacks. We consider that brief interstadial periods during maximal glacial creates most favourable conditions for initiation of caldera-forming eruption, largely through its influence on surface topography by glacial action, mass wasting, and influencing magma vesiculation/discharge as a function of rapidly changing overload.
机译：有人提出，冰川融化影响了世界上几个地区的火山活动，提高了地幔融化和地壳岩浆室爆发的生产力。但是，冰川和火山活动之间的联系并不直接。对堪察加冰川弧线中过去一百万年的火山口形成的Ar-Ar，U-Pb和C〜（14）年龄的研究导致观察到，大多数大体积的火成岩与形态保存完好的破火山口在时间上与过去几个冰川周期的“最大冰川”条件相对应。在该领域，主要证据与以下事实有关：冰川化的多火山口火山带有厚厚的冰川冰盖。其他证据来自于堪察加半岛衍生的海洋灰分层和DSDP岩心中的冰川冰cluster。在这里，我们提供了一组使用有限元方法进行数值模拟的新结果，这些结果研究了冰川负荷动态如何影响此类冰川多火山口火山环形成的条件。通过以下方式模拟了不同的情景：（1）现有冰盖的厚度和不对称分布；（2）导致随后坍塌事件的岩浆储层的深度和大小；（3）屋顶的厚度和力学性能（4）较深和较宽的岩浆储层的存在，以及（5）可能的重力破坏，其部分原因是由于冰下岩体的堆积和热液蚀变而引起的岩石破裂。得到的结果表明：（1）任何冰盖都对环断层的形成起作用； （2）冰的不对称分布可能有利于活板门式塌陷破火山口的形成； （3）部分火山构造的冰川侵蚀或冰川间构造的破坏可能有助于随后形成环断层； （4）冰盖下的热液系统可能导致火山口内顶板岩发生非常有效的热液腐烂，从而导致其力学性能发生变化并抑制/偏转环裂的扩展； （5）陆间期受冰川侵蚀和冰量变化影响的岩石表面形貌/负荷。尽管对应力场的分析可能会告诉我们有关环断裂引发的可能性，但它不能确保其完全传播。这里还将讨论控制这种现象的参数。总的来说，最大冰川时间代表了多火山口火山生命中最活跃的时间（与更安静的冰川间相比），促进了物理和化学反馈。我们认为，最大冰川期的短暂内陆期为火山口形成喷发的开始创造了最有利的条件，这主要是由于冰川作用，物质浪费以及作为快速变化的超负荷作用而对岩浆囊泡化/排放的影响。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号