Fig. 2: Hydrothermal systems and lava–water interactions.
From: Young volcanic terrains are windows into early microbial colonization
a Long-lived bicarbonate rich springs in the Geysir geothermal area, Iceland (photo credit: N. Hadland)236. b Long-lived acid-sulfate springs in the Krýsuvík geothermal area, Iceland (Photo credit: N. Hadland)176. c Ephemeral hot springs that formed following the 2014–2015 Holuhraun eruption in Iceland after the lava was emplaced into the Jökulsá á Fjöllum river (Photo credit: C. W. Hamilton). d Meteoric water percolating through permeable basalt to a hot center in a lava flow resulted in ephemeral fumaroles that lasted for several years after the 2018 Kīlauea eruption in Hawaiʻi (Photo credit: N. Hadland). e Evidence of past hydrothermal activity on Mars in the form of white nodular opaline silica deposits (amorphous SiO2 · nH2O) (Mars Exploration Rover Spirit Pancam false-color image P2388; Photo credit: NASA/JPL-Caltech)93. f Chains of ring-mound landforms in Athabasca Valles on Mars, which are interpreted to be volcanic rootless cones formed by explosive lava–water interaction. The overlapping cones indicate the features in the upflow direction (black arrow) are younger237 (High Resolution Imaging Science Experiment (HiRISE) image PSP_002938_1890; Photo credit: NASA/JPL-Caltech/UArizona).
