The region to the east of mare Humorum has many rilles. The Hippalus rille system (upper part of image) curves around the mare and was formed by crustal stretching as the weight of the mare depressed the surface. There is a complex system of intersecting rilles around the small crater Ramsden, lower centre. Finally, the linear Hesiodus rille extends from just north of the crater Capuanus and out of the frame to the upper right.