GSA Today
Volume 19, Number 11 (November 2009)

About the cover:
Modern microbial mat on a sandy depositional surface (photo by Nora Noffke). In modern tidal environments, benthic cyanobacteria form carpet-like microbial mats of sometimes square kilometers in extent—one of Earth’s largest ecosystems. The interaction of sediment-stabilizing microbial mats with the physical sediment dynamics causes the characteristic “microbially induced sedimentary structures” (MISS). See “Geobiology: Evidence for Early Life on Earth and the Search for Life on Other Planets” by S.L. Cady and N. Noffke, p. 4–10.