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

灾难性的火山口形成喷发是地球上最令人敬畏的自然现象之一。在喷发期间，数千立方公里非常粘稠和富含晶体的岩浆在几天到几周的时间范围内爆炸式地喷发。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。人们认为，为这些所谓的“超级火山喷发”提供动力的岩浆，部分来自高层岩浆室，部分原因是致密岩浆室顶板与时间相关的活塞式下沉，进入了下方密度较低的横向分布的或部分熔融的岩浆室。尽管这种喷发的数量可能并不令人惊讶，因为它们预计会一直持续到大部分或所有浮力岩浆被驱逐出去，但对喷发速度的极端解释仍然是火山学中最引人注目的问题之一。具体而言，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坚固、可变形的多孔介质的快速压实和解聚。破坏和排出这种物质所固有的机械困难对潜在的岩浆室过程提出了限制要求。这一提议采用了现场观察、实验室流体动力学实验、理论工作和数值模拟的新颖组合，以确定和理解使如此大量的富含晶体的物质如此迅速地喷发的岩浆室动力学。

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.