The easy mobility of strongly chemisorbed species on metal surface is in apparent contradiction with successive ruptures and formations of strong bonds implying high energy barriers. We show that adsorption energy is by far (two orders of magnitude) larger than the energy allowing a shift of the surface metallic layer upon those beneath. Thus, an oxygen migration preserving strong oxygen-metal bonds by a slipping motion of the metal atoms beneath is energetically favorable. Strong surface restructuring occurs in heterogeneous catalysis whenever strongly bounded adsorbates are involved. (C) 2008 Elsevier B.V. All rights reserved.