The second AUV mission took place at ~2500 mWD on the western
flank of the MCSC, and covered an area of 1.5 × 3.0 km in 28 h with a
track line spacing of 75m. A number of distinct Eh signalswere detected
over the summit of a conical-shapedmound,which is 130min diameter
and 50 m high (Fig. 4D–E). The unusual shape of the mound and its
association with strong Eh signals indicated that it was a site of active
hydrothermal fluid emission, subsequently termed the Von Damm
Vent Field. With the target site located, the ROV was again deployed
to investigate visually, and sample the substratumand fauna. As a result,
the conical moundwas confirmed as a site of voluminous hydrothermal
fluid emissions and host to abundant vent-specific fauna (Connelly
et al., 2010). Overall, these data highlight the benefits of using a nested
multi-resolution survey approach, for efficient discovery and characterisation
of active hydrothermal vent sites in the deep ocean.