The North Arch volcanic field lies north of Oahu at depth; within the Exclusive Economic Zone of the Hawaiian Islands. The existence of lava flows in this geological region was already postulated in 1964, but it was GLORIA sidescan sonar eventually identified an anomalously reflective seafloor that constitutes the North Arch volcanic field; the discovery was first published in 1968 and rock samples taken in 1988. The volcanic field lies on the Hawaiian Arch and on its southern slope.