Southern EPR-Segment J

The axial crest of Segment J of the Southern East Pacific Rise consists of an asymmetrical shallow graben varying from 250 to 600 m wide with walls about 20 m high. Horst and graben structures expose cooled lava lakes and both active and extinct hydrothermal chimneys. Basaltic lava flow fields, lava pillars, and pillow mounds are found on the floor of the graben. The largest lava flow field is the Moai lava flow at about 18°12'S. Two lava flows have been dated by paleomagnetic evidence at about 1820 and 1890 CE.