Temperature-dependent surface morphologies of Si(100) resulting from Br etching at 700 and 800 K have been studied using scanning tunneling microscopy. Quantitative analysis of Linear pit distributions allows us to interpret the mechanisms involved in surface pattern formation. We show that linear chains growing at 800 K on 450-Angstrom-wide terraces are in quasi-steady-state conditions in that their lengths follow the most probable Flory-Schulz distribution. Results obtained under equivalent conditions at 700 K, however, demonstrate that this distribution is not reached. The difference reflects the rate of step retreat relative to the rate of pit growth. At 700 K, pits that develop on terraces are erased before their length distributions reach quasi-steady-state values even though the overall morphology does not change. The surface morphologies that are reached at long times can then be understood by considering the temporal evolution of linear chains on terraces where quasi-steady-state conditions are not fulfilled.