Novel strain-relief mechanisms for Ge/Si(100) coherent islands were identified. Ge/Si(100) islands were grown at temperatures, T, between 450 and 650°C for effective Ge coverages between 3.5 and 14.0 monolayers. The mean dome size increased and island dislocation was delayed as T increased. For T > 600°C, very large hut clusters populated a peak in island size distributions distinct from and between those of huts and domes. For T > 550°C, large dome clusters may form trenches at their base which extend well into the Si substrate. Increasing T reduced the island size for trench formation. Cross-sectional energy dispersive xray nanoanalysis confirmed that Si diffuses into the Ge clusters at T ≥ 550°C. Si interdiffusion was responsible for the increase in dome size and delay of dislocation with increasing T and the existence of very large hut clusters. AFM cross-sections indicate that there is a linear trench depth dependence on island size. A simple atomistic elastic model suggests that this experimentally observed self-limiting trench depth is kinetic rather than energetic in origin.