Bacterial mats coating spires at edge of primary fissure. Organ pipe high-temperature vent. Extensive hydrothermal precipitate on young lineated sheet flows. Old sulfide chimney at contact between young sheet flow and older lobate flow. Chimney is hollow.
Black coating is either lava spatter or manganese.
Across any particular cross section, all the venting is located either within the main fissure system, or within a few tens of meters from the fissure. On a subsequent visit in 1991, the venting had become so diffuse that it was no longer possible to obtain a vent fluid sample for analysis. Two or three closely spaced fissures occur in this area, but only one is actively venting on any cross section. It lies about 10 m west of the contact with the age 2 pillow mounds. The Monolith vent is the most robust of the high-temperature vents found at the north Cleft segment.