Silicic lava effusion controlled by the transition from viscous magma flow to friction controlled flow
Silicic lava effusion controlled by the transition from viscous magma flow to friction controlled flow
复制标题
由粘性岩浆流到摩擦控制流的转变控制硅质熔岩喷流
DOI：
10.1002/2017gl072875
复制
发表时间：
2017
影响因子：
5.2
通讯作者：
Tomofumi Kozono
中科院分区：
文献类型：
--
作者：
Satoshi Okumura;Tomofumi Kozono
硅质岩浆在火山导管中通过脆性-韧性转变形成垂直断层。断层的形成使流动类型由粘性流动转变为摩擦控制流动。在这里，我们通过将一维管道流动模型与实验校准的脆性-韧性转变相结合来研究岩浆的流动动力学。数值模拟结果表明，由于岩浆的结晶动力学和韧脆转变，摩擦控制流成为主要流动类型的岩浆塞长度取决于岩浆流量。在高通量时，由于非平衡结晶抑制了岩浆粘度的增加，形成了短栓。这导致在导管的浅部流出粘性较低的熔岩和较大的剪切应力。而在低通量条件下形成的长堵头，由于岩浆断层的软弱，无法维持较大的剪切应力，从而挤压出凝固的熔岩脊。
Silicic magma forms a vertical fault in volcanic conduits via the brittle‐ductile transition. The formation of the fault changes flow type from viscous flow to friction controlled flow. Here we investigate flow dynamics of magma by coupling a one‐dimensional conduit flow model with an experimentally calibrated brittle‐ductile transition. The numerical simulation demonstrates that the length of magma plug at which friction controlled flow becomes the main flow type depends on magma flux, because of crystallization kinetics and the ductile‐brittle transition. At high flux, a short plug forms, because nonequilibrium crystallization inhibits an increase of magma viscosity. This results in the effusion of less viscous lava and large shear stress at the shallow part of the conduit. In contrast, the long plug that forms under low flux cannot maintain large shear stress due to weakness of the magmatic fault, which causes the extrusion of a solidified lava spine.