Pointillistic features from the wall of Epperson's Cave. (A) Two-centimeter overview of macroscopic deposits. Image courtesy of Kenneth Ingham; used with permission. (B) Overview of iron-oxide biofilm with unerupted colonies. (C) Scanning electron micrograph close-up view of the iron-oxide (FeOX) biofilm with colonies that are getting ready to erupt. (D) Newly erupted colony.