Lunar volcanism: Mare ridges and sinuous rilles, part P

Additional evidence of the volcanic origin of mare ridges and sinuous rilles is provided by near-terminator photography of the Herigonius Rille area (12 deg S 37 deg W) northeast of Gassendi Crater. A possible genetic relationship between ridges and rilles is illustrated. From the figure, the following relationships are evident. (1) The most prominent rille crosses several ridges without distortion, which indicates that the mare ridges did not form after the sinuous rilles. (2) The rilles could not have formed by flow up and over the ridges. (3) The rilles extend from their widest ends toward distinctly lower elevations, and the largest one branches both north and south from the vent area. Elevations are evident in stereographic views that clearly indicate the local slopes. (4) The wider end of each rille is marked by an elongate vent (?) near the summit of the mare ridge from which the rille appears to issue. (5) The two most prominent rilles join south of the vent area and continue southward for more than 130 km.