Channel flow has been proposed as a mechanism to explain the formation of the Greater Himalayan Sequence that is bounded by normal sense ductile shear along the Himalayan orogen. The key requirements for channel flow are: (i) extruding middle-to-lower crust of low viscosity, and (ii) excess gravitational potential due to topography. We present scaled two-layer physical models where the effect of the gravitational potential with respect to the plate convergence rate is investigated. Viscous middle crust starts moving towards the surface where the strain rate imposed by the convergence is 30% of that arising from the lateral pressure gradient. How efficiently the low-viscosity crust extrudes is directly linked to the imposed pressure gradient. A simple correlation between the extruding rock’s viscosity, the convergence rate, and the topography imposing the pressure gradient is established. The upward motion of viscous material is expected already for a mid-crustal viscosity of 10²¹ Pa s. This is significantly higher than previously expected, suggesting that one of the fundamental requirements for channel flow might not be necessary.

河道流已被提议作为解释大喜马拉雅层序形成的一种机制，该层序受沿喜马拉雅造山带的正常意义上的韧性剪切约束。通道流动的关键要求是：(i) 挤压低粘度的中下地壳，以及 (ii) 由于地形而产生的过量重力势。我们提出了缩放的两层物理模型，其中研究了重力势对板块收敛速度的影响。粘性中地壳开始向地表移动，在那里收敛施加的应变速率是侧向压力梯度产生的应变速率的 30%。低粘度外壳挤出的效率与施加的压力梯度直接相关。挤压岩石的粘度与收敛速度之间的简单相关性，并建立了施加压力梯度的地形。对于 10 的中地壳粘度，粘性材料的向上运动预计已经²¹ 帕秒。这明显高于之前的预期，表明可能不需要通道流量的一项基本要求。