Zealandia Bank consists of two pinnacles about 1 km apart rising from a submerged bank to near the ocean surface between Guguan and Sarigan Islands. One pinnacle reaches more than 1 m above water at low tide. Andesitic rocks were dredged at the southern peak, which showed some evidence of coral growth. Freshly broken pahoehoe basaltic rocks were recovered from 1.7 km depth on the western flank. The age of the most recent eruptive activity is not known, but a NOAA bathymetric survey in 2004 detected fumarolic activity.