Magma Chamber Growth During Intercaldera Periods: Insights From Thermo‐Mechanical Modeling With Applications to Laguna del Maule, Campi Flegrei, Santorini, and Aso
Magma Chamber Growth During Intercaldera Periods: Insights From Thermo‐Mechanical Modeling With Applications to Laguna del Maule, Campi Flegrei, Santorini, and Aso
复制标题
DOI：
10.1029/2018gc008103
复制
发表时间：
2019-03
期刊：
影响因子：
3.7
通讯作者：
M. Townsend;C. Huber;W. Degruyter;O. Bachmann
中科院分区：
文献类型：
--
作者：
M. Townsend;C. Huber;W. Degruyter;O. Bachmann
地壳岩浆室可以扩大到数百到数千立方千米，潜在地为灾难性的火山口形成喷发提供食物。体积较小的岩浆室预计会频繁喷发并迅速冻结；一个主要悬而未决的问题是，岩浆室如何增长到维持地球上最大的喷发所需的大小。我们使用热力学模型来研究控制洞室中挤出物：侵入比的主要因素，以及这与喷发频率、喷发大小和洞室长期增长的关系。该模型由三个基本时标组成：岩浆注入时标τin、冷却时标τCool和地壳粘性松弛时标τRelax。我们使用四座火山(拉古纳德尔莫勒火山、坎皮弗莱格雷火山、圣托里尼火山和阿索火山)的地质和地球物理数据来估计这些时间尺度，以将它们与模型进行比较。在这些系统中的每一个中，τin都比τCool短得多，比τRelax略短，在模型中，这些条件与有效的腔体生长和同时爆发有关。此外，该模型表明，这些火山下面的岩浆室正在以每年约10−4到10−2 km~3的速度增长，随着岩浆室体积的增加而加快。我们发现了喷发频率和喷发大小的比例关系，表明随着房间的扩大和挥发物的释放，喷发频率降低，但喷发大小增加。这些比例关系与自然系统的喷发历史很好地匹配，表明这些关系可以用来仅从喷发历史来限制洞室的增长速度和挥发的饱和状态。
Crustal magma chambers can grow to be hundreds to thousands of cubic kilometers, potentially feeding catastrophic caldera‐forming eruptions. Smaller volume chambers are expected to erupt frequently and freeze quickly; a major outstanding question is how magma chambers ever grow to the sizes required to sustain the largest eruptions on Earth. We use a thermo‐mechanical model to investigate the primary factors that govern the extrusive:intrusive ratio in a chamber, and how this relates to eruption frequency, eruption size, and long‐term chamber growth. The model consists of three fundamental timescales: the magma injection timescale τin, the cooling timescale τcool, and the timescale for viscous relaxation of the crust τrelax. We estimate these timescales using geologic and geophysical data from four volcanoes (Laguna del Maule, Campi Flegrei, Santorini, and Aso) to compare them with the model. In each of these systems, τin is much shorter than τcool and slightly shorter than τrelax, conditions that in the model are associated with efficient chamber growth and simultaneous eruption. In addition, the model suggests that the magma chambers underlying these volcanoes are growing at rates between ~10−4 and 10−2 km3/year, speeding up over time as the chamber volume increases. We find scaling relationships for eruption frequency and size that suggest that as chambers grow and volatiles exsolve, eruption frequency decreases but eruption size increases. These scaling relationships provide a good match to the eruptive history from the natural systems, suggesting that the relationships can be used to constrain chamber growth rates and volatile saturation state from the eruptive history alone.