The Lunar Alps

A portion from LROC Narrow Angle Camera oblique mosaic M177602135LR, and a rille, seen in the center of this image, running northwest to southeast through the Montes Alpes northwest of Mare Imbrium. Field of view approximately 15 km (north to the right). Spacecraft orbit 11309, December 4, 2011; average resolution 3.12 meters per pixel from 41.6 km over 49.86°N, 4.3°E [NASA/GSFC/Arizona State University].

H. Meyer
LROC News System

Rilles are common on the Moon and are considered one of the most fascinating volcanic features due to their wide range of scales (100's of meters to over 100 kilometers in length) and morphologies they present (linear, arcuate, 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.

An uncorrected full resolution stitch of LROC NAC mosaic M177602135LR, allowing a false perspective on the rille of interest, west of the spacecraft's orbital track [NASA/GSFC/Arizona State University].

A lower resolution, corrected view of the full LROC NAC oblique. The rille discussed in LROC Featured Image released November 15, 2013 indicated by white arrows [NASA/GSFC/Arizona State University].

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.

LROC WAC image of Montes Alpes; field of view approximately 500 km across, centered at 49.397°N, 358.731°E. LROC Featured Image area outlined by the red rectangle [NASA/GSFC/Arizona State University].

Montes Alpes, named by the Polish astronomer Johannes Hevelius, is a mountain range formed by the Imbrium impact event, stretching from the crater Plato all the way to the Montes Caucasus. It forms part of the northeastern border between Mare Imbrium and Mare Frigoris. The Montes Alpes range is bisected by Vallis Alpes ("Alpine Valley"), a flat-bottomed valley with a rille running right down the center from Mare Imbrium to Mare Frigoris that can be seen in the WAC context image above. The Montes Alpes separate the two mare; however, Vallis Alpes breaches that boundary. What might that mean for the geologic history of this area?

Explore Montes Alpes and the rille for yourself HERE.

Related Posts:
Discontinuous Rilles
Old Man River (of Lava!)
Montes Pyrenaeus meets Mare Nectaris