We propose to characterize the response of continental biosphere to large extraterrestrial impact craters, in particular the megafires they may have generated, associated with the melting of the Earth surface. Studying the impact glasses ejected at long distance, called tektite, will be instrumental in the project. Three tektite producing impacts occurring on forested tropical surfaces from Nicaragua, Ghana, and Indochina during the last 1.1 Myr will be investigated. Environmental response to impact, probed by pollen, charcoal and other proxies will be studied in various marine and lacustrine archives. Reaction of impact melt with biomass (elements such as C, P, S) will be traced using compositional variability of tektites explored in a systematic way, as well as nano-scale characterization of inclusions in tektites such as phosphates, metal, iron oxydes, and eventual carbon phases. This will bring new clues on tektite production processes and response of ecosystems to megafires.