  A criterium is derived to understand the relevance of thermal effects
resulting from high rate mechanical actions on glass surface. The criterium is
based on the concept of characteristic contact time of the load to the glass
surface. This criterium is of particular relevance to impact phenomena. A
general discussion about dissipative aspects of indentation on glass surface is
presented and a thermodynamic approach is suggested to evaluate the energetic
of the process. Further generalization is proposed based on the thermodynamics
of continuous media.
