We use atom-resolved scanning tunneling microscopy (STM) to investigate in the real space, the effects of slight contamination on the beta-SiC(100) surface structure. We find that a 2 X 1 surface ordering is induced by background surface contamination of the c(4 X 2) surface reconstruction. This results from the disruption of the latter having alternately up- and down-dimer (AUDD) ordering, with all dimers coming at the same height, leading to adsorbate-induced electronic redistribution. This work, which stresses the very high surface sensitivity of the beta-SiC(100) c(4 X 2) surface reconstruction, is especially relevant in achieving high quality "well defined" beta-SiC(100) surfaces.