Hadley Rille (from Orbit)
This photo shows the Hadley Rille on the southeast edge of Mare Imbrium.
It is fairly well known because Apollo 15 landed there (see next image).
The rille begins at the curved gash in the bottom left corner, and is
clearest in the rectangular, mare-floored valley shown here. In the upper
left, it gets much shallower and it slowly fades out of sight in Palus
Putredinis. In all, the rille is over 75 miles (120 km) long. It is up to
5000 feet (1500 m)
across and is over 950 feet (300 m) deep in places. It formed nearly 3.3
years ago . In contrast, lava channels on Hawaii are usually under 6
miles (10 km)
long and are only 150 - 300 feet (50-100 m) wide. This contrast in channel
reflects (1) differences in the volume of erupted lava and (2) the
difference in gravity. Note -- The bright bumps surrounding Hadley are
peaks of the Montes Apenninus. These mountains mark the edge of the impact
basin holding Mare Imbrium. They rise from 6000 to 15,000 feet (1800
- 4500 m) above the
mare. (Apollo 15 image M-1135, arrow marks landing site of Apollo 15.
Image taken from NASA SP-469, Geology of the Terrestrial Planets)