Airy isostasy has been observed in many active orogenic regions including Himalayas/Tibetan plateau and Tian Shan. To better understand the temporal evolution of mountain building, we investigate how topography at the surface and crust-mantle boundary (i.e., Moho) that evolves in response to crustal shortening depends on mechanical properties of continental lithosphere. Our dynamic models reveal that if the effective viscosity of continental lithosphere is less than 100 times of the viscosity of the underlying mantle, orogenic belts and their corresponding roots at Moho can grow simultaneously with the Airy isostasy being approximately maintained. This result is consistent with the relatively small viscosity inferred for continental lithosphere of actively deforming central Asia regions including Tibetan plateau. ¿ 2000 American Geophysical Union