Fig. 5: Mechanisms for microbial deposition in volcanic terrains.

a Syn-emplacement mechanism for soil deposition on the surface of lava. In the foreground, lava scraped or bulldozed underlying soil followed by an inflationary process that lofted particles onto the surface of the flow. Saturated soils also flashed to steam as lava flowed over the substrate, carrying soil particles as the steam escaped through cracks. Dusty steam plumes are visible at the back of the image. Image from the 2021 Fagradasfjall eruption, Iceland (Photo credit: C. W. Hamilton). b Finer-grained soil particles have been blown onto the surface of lava at Fagradasfjall post lava emplacement (Photo credit: N. Hadland). c Wet sediment deposited onto the surface and interior of the lava from fluvial systems. Image of the 2014–2015 Holuhraun lava flow field, Iceland (Photo credit: C. W. Hamilton). d At Holuhraun, coarser-grained sand has been blown up against the side of the lava flow, progressively building up sand ramps to deposit material on the surface of the flow and even cover portions (Photo credit: N. Hadland). e Snow and rain fell on Fagradasfjall lava during emplacement, potentially carrying microorganisms (Photo credit: C. W. Hamilton). f Human and animal visitors to lava flows, such as shown here at Fagradasfjall, can also bring microbial colonizers (Photo credit: C. W. Hamilton).