The geoarchaeology evaluation of the Monumento Nacional Guayabo (M.N.G.) shows the following problems: the water, with pH 5,5-6,0 or 7, flows over the rocks paths, it is a chronic problem, the cause could be springs, aqueduct collapse, poor soil infiltration. The low pH, could cause colored precipitates. The abundant flora, like lichens, have covered the rock and other geoarchaeological features. The lichens could damage the lithic and glyphs. The geological study, shows regional and big landslides, but the M.N.G. seems to be stable and there are not in the Monument itself. The petrography shows a basaltic-andesite rocks with glass matrix. It means that the rock is easily eroded. The fluidal texture produces natural laminations. It is means no harmful rocks just it is a natural feature.

petrografía; andesita-basáltica; geoarqueología; volcán Turrialba; lahares; deslizamientos; litología; líquenes