裂谷和地堑的形成看来是由地壳的偏拉张引起正断层活动而造成的。在理想的情况下,当邻近区域向上弯曲形成地堑的边缘隆起时,两个向内倾的正断层使得其间向下变窄的断块下沉。断层可以是平面状的,但它们也可以在深处变缓形成铲形。假如只发育一个断层,那么,就形成半地堑。 The formation of rifts and grabens appears to be caused by the normal faulting caused by the delaminations of the crust. In the ideal case, two inwardly leaning normal faults allow the faulted blocks that narrow downwards between them to sink when the adjacent area is bent upwards to form the edge of the graben. Faults can be planar, but they can also slow down to form a scoop. If only one fault is developed, then a half-graben is formed.