A study of the seafloor in the North Fiji Basin is leading to a better understanding of the geometry and evolution of spreading in back‐arc basins. Two of the most important features of the area, the South Pandora Ridge and the Tripartite Ridge, belong to a presently active spreading system that began forming at least 7.2 m.y.a. The ridges spread at an average rate of about 1.6 cm/yr. By studying the segments of the ridges in greater detail, researchers found that each was either a “tectonic type,” with a more or less complex deep axial valley, or a “volcanic type,” with a high, rifted volcanic massif occupying the axial domain.