An essential task in geomicrobiology is to understand how newly formed substrates become colonized by microbial communities, which may ultimately play a role in rock weathering, soil formation and ecosystem development. Volcanic eruptions offer numerous opportunities to increase our understanding of terrestrial ecosystem formation. However, very few teams have been able to collect samples and data at early stages of volcanic substrate formation. Most studies have started their samplings years, often decades to hundreds of years after the eruption (i.e., well after the establishment of microbial communities), and only one study was able to gather data three months after the eruption. Therefore, very little is known about the initial colonists of freshly deposited volcanic rocks, particularly at high latitudes. On March 19th 2021, the new volcanic eruption near Mount Fagradalsfjall, on the Reykjanes Peninsula in Southwest Iceland, began extruding a fresh lava flow. Studying the initial colonists of the freshly deposited volcanic rock from the onset of its formation represents a unique opportunity to answer many questions about the microbial succession and community establishment of new ecosystems. This project will acquire samples and data for microbial, geochemical and physicochemical characterization of the new ecosystem formation. Considering this rare chance for an immediate sampling of a fresh lava flow, this work has the potential to transform our understanding of microbial community succession from a sterile environment to an established and resilient community. This project will also train one graduate student in field sampling and laboratory analyses. Results from this effort will be made publicly available shortly after sample and data collection. The graduate student and the investigator will give public lectures about the work. They will also coordinate with the U.S. Embassy in Iceland and Fulbright ? Iceland Commission to promote the RAPID response by U.S. researchers in Iceland. The project seeks to answer fundamental questions about the initial colonists of freshly deposited volcanic rocks: 1-What is the taxonomic diversity of the earliest colonists of volcanic rocks and how does it change over time? 2-What are the potential sources of colonizers? 3-What are the metabolic capabilities of these early colonists? Being in Iceland before, during and at least 5 months after the start of the Fagradalsfjall volcanic eruption, affords the investigator a rare opportunity to collect pre-, and post-eruption samples and data to answer these questions. Two hypotheses will be tested: (H1) early colonizers of the volcanic rock will be present in low abundance, low taxonomic diversity and rely on photo- and/or chemolithotrophic metabolism and (H2) the volcanic rock will harbor an increasingly complex microbial community in terms of diversity and function over time, including organoheterophs and photoautotrophs, after only a few months. The project will acquire samples and data for microbial, geochemical and physicochemical characterization of the new ecosystem formation. The new discoveries resulting from this study would set the stage for further research that will analyze the samples with sequencing and geochemical approaches and extend the study over a longer period (years). The research will provide urgently needed evidence to examine how newly formed volcanic substrates become colonized by microbial communities, looking specifically at the taxonomic identity and functional capabilities of early colonists but also at their external sources. To examine the origin of early colonists they will also collect samples from water, rock, soil and bioaerosols as part of the RAPID response. In the follow up study, they will use next-generation sequencing-based microbial source tracking to estimate the source of microbes found to occupy the newly formed lava flows. The research products will be of interest to a number of other fields outside the immediate field, specifically fields seeking a mechanistic understanding of interactions between microbial populations and their environment, and the emergent properties of the complex community. The new culture isolates will also provide information on the roles of early colonizers in elemental cycles, geobiology, and biochemistry. This project will support the travel of a graduate student to perform field work in Iceland and to process samples for return to his Institution. Results from this work will be a key focus of his Ph.D. research. Results from this effort will be disseminated through publications, public databases, and public lectures. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.