The 500-m-long Mothra hydrothermal field is the largest venting site in areal extent on the Endeavour segment of the Juan de Fuca Ridge. Within this field, there are at least five actively venting sulfide complexes, spaced 40 to 200 m apart along a trend of 020. The clusters are composed of multiple steep-sided pinnacles that rise up to 20 m above the seafloor. Most of the sulfide structures are awash in diffusely venting fluids (30–200 °C) that support rich and diverse macrofaunal and microbial communities. Isolated black smoker chimneys vent 302 °C fluids. The linear arrays of sulfide complexes delineate a zone of active faulting near the western wall of the axial valley. This fault network serves as the conduit for the rising fluids.

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