Tilted block: thrust faults have been interpreted to bound tilted blocks on Io. Tilted blocks have a polygonal shape and curved crests. One example is Euboea Montes. A terrestrial analogy is the Black Hills of South Dakota. Mass wasting: several types of mass movement deposits have been observed adjacent to Ionian mountains. Downslope movements of blocks have been noted in at least one place, the Euboea Montes. Fan-shaped deposits resembling debris aprons are found at the base of steep slopes. The ridged or crenulated surfaces of some mountains like northern Hi'iaka Montes may be formed by downslope creep of layered rock. Layered crust: the upper Ionian crust may be layered, as suggested by flowing observations: mountain uplifted and exposed crust section at Euboea Montes, different colored units exposed on Haemus Mons, a ridged unit atop northern Hi'iaka Montes, and striations on mountains such as Haemus Mons and Tohil Mons. Stresses Stress plays an important role in the origin of Io's mountains. Various kinds of stresses are considered to be responsible for the deformation of the lithosphere. Folding and faulting form all kinds of topographic features on Io. Overburden stress: on Io, the resurfacing process keeps forming new layers at the surface and pushing older layer downwards. Overburden stress is stress imposed on an older layer of rock by the weight of overlying younger layer of rock. The horizontal stress () generated is less than the vertical overburden () by a factor of /(1- ),where is Poisson's ratio (value is 0.25 for rock)/ref>. The differential stress is ()-(). This tensile stress is insufficient to cause faulting on Io, because the value is less than Byerlee's rule for rock failure in extension. However, the overburden stress may contribute to the faulting when combined with other stresses Subsidence stress: continuous burial of older crust by younger crust causes older rock to be pushed inward to a sphere with a smaller radius. This subsidence of older crust may imply enormous horizontal compressive stress. This stress is related to resurfacing rate (v), Io's radius (R), subsidence distance (ΔR) and Yong's modulus. The subsidence-generated horizontal stress is equal to E/(1-V)× ΔR/R. This stress is more than enough to cause faulting on Io. Thermal stress: thermal stress is another possible stress source on Io, as increasing temperature in Io's crust can cause expansion of the crust. The total tidal heating generated in Io is dissipated to resurfacing