山崖的陡立面。 崖壁的生成条件主要包括以下四个方面： 1.岩层中垂直节理发育。张家界的石英砂岩垂直节理十分发育。 2.岩性坚硬。张家界的石英砂岩主要矿物是硬度较高的石英。 3.岩层抬升幅度大。张家界区域经过了多次地壳运动使得砂岩地层得以多次被抬升。 4.外力作用强烈。张家界崖壁形成的外力作用主要是流水下切、重力崩塌作用、生化作用和物理风化作用。  This is the steep face of a cliff. The formation of a cliff requires the following conditions: 1.Developed vertical joints in the rock stratum. Vertical joints are very well-developed in the quartz sandstone in Zhangjiajie. 2.Hard lithologic character. The main mineral composing the quartz sandstone in Zhangjiajie is quartz, which is of high hardness. 3.Big range of stratum uplift. Zhangjiajie area went through multiple crustal movements though its sandstone stratum was uplifted for multiple times. 4.Intense exogenic action. The exogenic processes causing the forming of the cliffs in Zhangjiajie mainly include undercutting by flowing water, gravitational collapse, biochemical action and physical weathering.