Rilles are common on the Moon and are considered one of the most fascinating volcanic features due to their wide range of scales (100s of meters to over 100 kilometers!) and morphologies they present (linear, arcuate (below), or sinuous). Rilles commonly form when lava flows erode into the existing surface through melting of the substrate, mechanical stripping away of material, or a combination of both thermal and mechanical processes. However, some rilles may have been lava tubes that underwent roof collapse since their formation.
In Today's Featured Image, lava carved into the surface between peaks of the Montes Alpes ("Alpine Mountains") and left behind a narrow, long depression resembling a meandering terrestrial river channel, complete with what appear to be cut-off meanders (called oxbows on Earth). In this case, the rille developed meanders as the lava flowed around topographic highs, which in this area are the Montes Alpes.
Explore Montes Alpes and the rille for yourself below!Related Posts:
Old Man River (of Lava!)
Montes Pyrenaeus meets Mare Nectaris
Back to Images