ABSTRACTBasaltic rocks play a significant role in CO2 sequestration from the atmosphere during their weathering. Moreover, the primary microorganisms that colonize them, by providing mineral elements and nutrients, are shown to promote growth of diverse heterotrophic communities and plants, therefore positively impacting Earth's long-term climate balance. However, the first steps of microbial colonization and subsequent rock weathering remain poorly understood, especially regarding microbial communities over a chronological sequence. Here, we analyzed the microbial communities inhabiting the soil developed in crevices on lava flows derived from different eruptions on Fogo Island. Investigated soils show typically low carbon and nitrogen content and are relatively similar to one another regarding their phylogenetic composition, and similar to what was recorded in large soil surveys with dominance of Actinobacteria and Proteobacteria. Moreover, our results suggest a stronger effect of the organic carbon than the lava flow age in shaping microbial communities as well as the possibility of exogenous sources of bacteria as important colonizers. Furthermore, archaea reach up to 8.4% of the total microbial community, dominated by the Soil Crenarchaeotic Group, including the ammonium-oxidizer Candidatus Nitrososphaera sp. Therefore, this group might be largely responsible for ammonia oxidation under the environmental conditions found on Fogo.