The micromechanics of strain localization in partially - molten silicic magma chambers: keys for understanding the origin, and dynamics of "supervolcanic" eruptions

部分熔融硅质岩浆房应变局部化的微观力学：理解“超级火山”喷发的起源和动力学的关键

• 批准号: 262856-2008
• 负责人: Jellinek, Andrew
• 金额: $ 2.19万
• 依托单位: University of British Columbia
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2011
• 资助国家: 加拿大
• 起止时间: 2011-01-01 至 2012-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=480249
• 关键词: micromechanics; strain; localization; partially; molten

Catastrophic caldera-forming eruptions during which thousands of cubic kilometers of very viscous and crystal-rich magma is erupted explosively over a time scale of days to weeks are among the most awesome natural phenomena on Earth. Such events have occurred intermittently throughout Earth's history in places such as the Yellowstone caldera, USA and in the Taupo volcanic zone, New Zealand. Magmas feeding these so-called "supervolcanic eruptions" are thought to be driven from high-level chambers, in part, by a time-dependent piston-like foundering of a dense chamber roof into an underlying laterally-extensive molten or partially-molten magma chamber of lower density. Whereas the volumes of such eruptions are perhaps not surprising, as they are expected to proceed until most or all buoyant magma is expelled, an explanation for the extreme rate of eruption remains one of the most compelling problems in volcanology. In detail, the physical problem governing the rate of eruption is analogous to the rapid compaction and disaggregation of a strong, deformable porous medium constructed of a solid crystalline matrix and a viscous interstitial pore fluid. The inherent mechanical difficulty with disrupting and expelling such a material places restrictive demands on the underlying magma chamber processes. This proposal uses a novel combination of field observations, laboratory fluid dynamics experiments, theoretical work and numerical simulations to identify and understand the magma chamber dynamics that enable such a large volume of crystal-rich material to be erupted so quickly.

在形成火山口的灾难性喷发中，数千立方公里非常粘稠且富含晶体的岩浆在几天到几周的时间内爆发，这是地球上最令人敬畏的自然现象之一。这样的事件在地球历史上断断续续地发生过，比如美国的黄石火山口和新西兰的陶波火山带。这些所谓的“超级火山爆发”的岩浆被认为是从高层的岩浆室中喷出的，部分原因是由于密集的岩浆室顶部像活塞一样随着时间的推移而下沉，进入了密度较低的横向广泛的熔融或部分熔融岩浆室。尽管这种喷发的规模也许并不令人惊讶，因为它们预计会持续到大部分或所有的浮力岩浆被排出，但对这种极端喷发速度的解释仍然是火山学中最引人注目的问题之一。具体来说，控制喷发速度的物理问题类似于由固体晶体基质和粘性间隙孔隙流体构成的强而可变形的多孔介质的快速压实和分解。破坏和排出这种物质的内在机械困难对潜在的岩浆房过程提出了限制性要求。这一建议采用了一种新颖的结合现场观测、实验室流体动力学实验、理论工作和数值模拟的方法来识别和理解岩浆室的动力学，使如此大量的富含晶体的物质能够如此迅速地喷发。