Hadley Rille/Apennine Mountains
26.13222° N latitude, 3.63386° E longitude
The Apollo 15 landing site was located at 26° 4' 54" north latitude by 3° 39' 30" east longitude at the foot of the Apennine mountain range. The Apennines rise up to more than 15,000 feet (4572 m) along the southeastern edge of Mare Imbrium (Sea of Rains).
The Apennine escarpment—highest on the Moon—is higher above the flatlands than the east face of the Sierra Nevadas in California and the Himalayan front rising above the plains of India and Nepal. The landing site had been selected to allow the astronauts to drive from the LM to the Apennine front during two of the EVAs.
Hadley Rille is a V-shaped gorge paralleling the Apennines along the eastern edge of Mare Imbrium. The rille meanders down from an elongated depression in the mountains and across the Palus Putredinis (Swamp of Decay), merging with a second rille about 62 miles (100 kilometers) to the north. Hadley Rille averages about a kilometer and a half in width and about 1,300 feet (400 meters) in depth throughout most of its length.
Large rocks have rolled down to the rille floor from fresh exposures of what are thought to be stratified mare beds along tops of the rille walls. Geologists were curious about the origin of the Moon's sinuous rilles, and some scientists believe the rilles were caused by some sort of fluid flow mechanism—possible volcanic.
Mount Hadley, Hadley Rille and the various Hadley craters in the region of the landing site are named for British scientist-mathematician John Hadley (1682-1744) who made improvements in reflector telescope design and invented the reflecting quadrant--an ancestor of the mariner's sextant.