Rilles and Wrinkle RidgesDescribe the nature of rilles and wrinkle ridges
Rilles are cracks or clefts on the lunar surface notably near maria.
They are geological faults caused by collapsed lava tubes. When lava flowed
on the Moon, the top and sides of these tubes solidified first while lava
flowed underneath. When this lava moved away or solidified, the top or
roof of the tube collapsed, leaving these rilles.
Wrinkle ridges are ridges of maria, usually hundreds of kilometres in length. They are not considered mountains, being only around 200 metres high.
These are thought to have been lava tunnels that contracted