Mare ridges often consist of two separate but related features: (1) a broad gentle arch overlain by (2) a sharper, more contorted ridge. Often these sharper, secondary ridges have flowed into craters in the adjacent terrain indicating they are extrusions. Major flows in Mare Imbrium appear to have issued from several prominent mare ridges. These flows show color differences which may be related to their abundance of titanium. The association of flows with mare ridges, the broad arching linked with many ridges and the coincidence of linear ridges with the directions of major fracture patterns in the highlands indicates that arched mare ridges are dike, sill or laccolithic-type intrusions along major fractures. In many cases these intrusions appear to have broken through the surface to form short flows and bulbous lava extrusions. Mare ridges unassociated with arching are probably lava extrusions only.
Mare ridges often take the form of rings indicating that they developed along ring fractures. Several linear mare ridges and mare ridge rings have bright hills situated along them and are considered to be post-mare volcanic hills of more siliceous composition than the maria. Evidence suggests that many of the ring structures are post-mare volcanic ring complexes formed over large igneous masses.