This review focuses on the geobiological importance of subaerial biofilms. They are the most rapid agents of destruction and wear-down of soil, rock and mountains. Further the exposure and reactions of organisms to most radical and extreme stresses and changes of environmental conditions at the rock surface are a crucial question in planetary biology. Poikilotroph organisms in poikilophilic environments especially the often underestimated black yeast are probably the most active rock destructive components of terrestrial ecosystems (Gorbushina and Krumbein, 2000). Expanding the tantalizing question: "How long is the Coast of England?” into four-dimensional space and time it emerges, that the reactive continental surface in terms of exchange between rock, soil, biota and atmosphere may be more then 3 orders of magnitude larger than the oceanic one. This attributes an important role to subaerial biofilms, networks and patina of rock, soil and ice surfaces. The global carbon budget (via biologically accelerated rock decay), the albedo and some important temperature and climate controlling effects of biogeomorphogenesis are considered. The continental aspects of geobiology (from the surface to rock crevices at the thermal compensation depth of about 3 km) are largely unknown and new territories for geobiological research. The microflorae involved and some of the global aspects of weathering and biomineral formation are presented and discussed (Gorbushina et al., 2001). New methods of study and differentiation of physical, chemical and biologically induced or accelerated weathering processes will be presented. Quantitative data on mere physical and chemical attack in comparison to biologically induced and catalyzed biotransformation and biotransfer processes are compared in laboratory and field experiments/examples. Gorbushina, AA, Krumbein, WE, 2000. In: Riding, RE, Awramik,. SM, Microbial Sediments, Springer, 161-170. Gorbushina, AA et al., 2001. Geomicrobiology Journal, 18, 117-132.