Effect of stress fields on magma chamber stability and the formation of collapse calderas
Effect of stress fields on magma chamber stability and the formation of collapse calderas
复制标题
应力场对岩浆房稳定性和塌陷火山口形成的影响
DOI：
10.1029/2002tc001369
复制
发表时间：
2003
期刊：
影响因子：
4.2
通讯作者：
M. Strecker
中科院分区：
文献类型：
--
作者：
W. Bosworth;K. Burke;M. Strecker
地球和其他行星上许多较大的火山的峰顶都被火山口占据，这些火山口是由于塌陷而形成的，形成了一个撤离的岩浆库。这些崩塌的火山口通常有几十平方公里的面积，通常呈椭圆形。研究表明，肯尼亚裂谷、西部盆地和山脉省、蛇河-黄石高原和冰岛裂谷的晚第四纪崩塌火山口长轴与上地壳最小水平应力方向（Sh）平行，这是由独立标准确定的。我们认为，这些火山下的圆形岩浆房是由应力引起的室壁剥落而变成椭圆形的，其机制类似于钻孔和隧道中突围的形成。在突围中，孔洞变得与远场最小应力平行。在肯尼亚裂谷，晚更新世破火山口崩塌伴随着45°的Sh旋转和最大水平应力（Sh）的增大。爆发模型预测，在这种条件下，火山口壁会变得越来越不稳定，这可能解释了为什么在火山环境中突然出现了这么多以前从未经历过的崩塌事件。这种应力变化诱发崩塌的机制可能在其他破火山口环境中也发挥了作用。
The summits of many of the Earth’s and other planets’ larger volcanoes are occupied by calderas that formed by collapse into an evacuating, underlying magma chamber. These collapse calderas are typically several tens of square kilometers in area and are commonly elliptical in shape. We show that the long axes of late Quaternary collapse calderas in the Kenya rift valley, the western Basin and Range province, the Snake River‐Yellowstone Plateau, and the Iceland rift zone are parallel to the upper crustal minimum horizontal stress direction (Sh) as determined by independent criteria. We suggest that circular magma chambers beneath these volcanoes became elliptical by stress‐induced spalling of their chamber walls, by a mechanism that is analogous to the formation of breakouts in boreholes and tunnels. In breakouts, the hole becomes elongate parallel to the far‐field minimum stress. In the Kenya rift, Late Pleistocene caldera collapse was accompanied by a 45° rotation of Sh and an increase in the magnitude of the maximum horizontal stress (SH). The breakout model predicts increasingly unstable caldera walls under these conditions, a possible explanation for the sudden appearance of so many collapse events in a volcanic setting that had never experienced them before. This mechanism of stress change‐induced collapse may have played a role in other caldera settings.