Volcanism on the Moon
By Robert Wickman
Sinuous rilles are probably the most recognizable of small volcanic
features on the Moon. Many partially resemble river valleys on the Earth.
However, the lunar rilles usually flow away from small pit structures.
Also, the lunar samples indicate that the Moon has always been bone dry.
Thus, the sinuous rilles probably mark lava channels or collapsed lava
tubes that formed during mare volcanism. Still, in some cases, the lunar
flows may have melted their way down into older rocks, much like rivers
their flood plains on Earth. Similar lava channels and tubes are found in
Hawaii, but these are all much, much smaller than those found on the Moon.