The southern East Pacific Rise (EPR) is the portion of the global mid-ocean ridge system where the great lithospheric plates comprising the ocean floor are separating at the fastest rates, approximately 15-16 cm/yr. In November, 1996, Rachel Haymon and Ken Macdonald conducted near-bottom surveys of the EPR crest between latitudes 17.3-18.5 deg. S using the DSL-120 kHz sonar system and the Argo II camera/sonar system. On left is an acoustic backscatter image showing a portion of the narrow (<50 m wide x 12 m deep) axial summit trough present along the ridge axis at 17 deg. 26'-29'S. On right is a co-registered record of the bathymetry of the same area [color changes at 5 m intervals betwee 2580 m (dark orange) and 2600 m (blue)]. The acoustic backscatter image reveals recent lava flows that breached the rim of the axial trough and spilled down the ridge flank. At center is an Argo photograph looking down on these new lava flows along the west rim of the axial trough (distance across photo = 10 m). The photo shows many animals attracted to volcanic hot springs within the trough.