NW Eifuku rises to 1,535 metres (5,036 ft) depth below sea level and is a 9 kilometres (5.6 mi) wide volcanic cone.

[11] NW Eifuku seamount rises to 1,535 metres (5,036 ft) depth below sea level[1] and has a roughly conical outline, with a basal width of 9 kilometres (5.6 mi).

[3] Rocks erupted by Eifuku range from basalt to andesite[1] that define either a potassium-rich calc-alkaline[15] or a tholeiitic suite.

[a][1] It lies west of the summit[18] in the sector collapse scar[1] and features both focused (white smokers that form chimneys) and diffuse venting.

The CO2 rises from the pumice and sulfur deposits on the ground[20] through crevices,[22] and it forms cold droplets with a milky skin[18] that stick to surfaces such as ROV tools.

They appear to originate from a layer underneath the ground surface, as disturbing the vent leads to increasing exhalations.

CO2 makes up about 87% of the droplets, which are rimmed by CO2 clathrates,[18] the concentrations per unit mass are about twice the solubility of CO2 under the environmental conditions[2] and considerably larger than at other known CO2 venting sites.

[14] Several ecological communities have been found at NW Eifuku, at 1,550 metres (5,090 ft) depth[2] and with distinct microbiotas:[34] The properties of exhaled fluids strongly influence the ecosystems surrounding hydrothermal vents,[41] and the environment of NW Eifuku has been used as an example for an ecosystem under heavy CO2 concentrations.

[42] Compared to other hydrothermal vent sites in the Pacific Ocean, mussels at NW Eifuku grow more slowly and have eroded shells, but they also are less subject to predation by crabs[43] and their body condition is not uniformly inferior.

[12] Barnacles, bivalves, nudibranchs, octocorals including bamboo corals, sea stars and sponges occur on Eifuku seamount.