The petrographic and petrophysical features of lavas and volcanic tuffs are very heterogeneous. They depend on: the original volcanic facies, the evolution during cooling, and the geomechanical stresses during movement. The natural outcropping rocks undergo weathering during the course of geological time; the causes and results are varied. Weathering also operates on objects worked by man from these materials when exposed to open air. This process is mainly dependent on climatic and microclimatic factors, since they control the hydrochemical and biochemical parameters. The authors emphasize the role played by marine spray. Technology transfer from previous studies allowed the development of a specific methodology to study volcanic materials in the broad sense and Easter Island statues in particular.