We study the evolution of surface morphology on Si(100) surface due to 60 keV Ar+-ion irradiation at room temperature for a wide range of ion fluences (2-80 x 10(17) ions cm(-2)) and angles of incidence (0 degrees-75 degrees). We have clearly distinguished linear and nonlinear regimes for the observed ripple patterns in our experiment. From our experimental results and those available in the literature, we have created a parametric phase diagram which summarizes an overview of pattern formation on silicon surface under medium energy ion irradiation. On the basis of this phase diagram, we demonstrate some striking similarities between medium and low energy ion-induced ripple patterns and infer that similar mechanisms may be responsible for pattern formation at both regimes. Comparison of our experimental results with numerical estimations reveals that both curvature dependent sputter erosion and ion induced atomic redistribution are responsible for the observed evolution of surface morphology. (C) 2014 Elsevier B.V. All rights reserved.