Supply Reef

Supply Reef is a submerged circular reef of volcanic origin in the Northern Mariana Islands chain, about 10 km NW of the Maug Islands. Presently, this igneous seamount is roughly 8 m below the ocean's surface and about 100 m in diameter. Apparent episodes of submarine volcanism were noted on December 22–24 and 26–27 in 1989.

Volcanic and seismic activity has been noted, as well as hard and soft corals.