|Hadley Rille was perhaps the most visually exciting feature we visited on any of our six lunar landing missions. Canyon-like, it meanders almost 70 miles across the lunar surface. From our point of view looking north, the rille is about 1100 feet deep and three quarters of a mile wide. We can see the sunlit far wall of the rille as it moves left to right just beyond Apollo 15 astronauts Dave Scott and Jim Irwin. It then turns northwest to disappear in the distance, it's east wall in shadow.
Dave had reported when they drove up in the rover a few minutes earlier, "man, you ought to have a great view on your T.V. This is unreal! The most beautiful thing I've ever seen." Joe Allen, the capcom in mission control agreed when the rover TV focused on the giant gouge in the Moon: "we have a view of the rille that is absolutely unearthly." Jim replied: "glad you can enjoy it with us", as he and Dave began their tasks.
Dave is using his hammer to knock small pieces off a lonely boulder. Dave felt the boulder might be significant because its isolation suggests it was blasted from deep within the Moon when a meteoroid impacted the surface some distance away. Jim is back at the rover, getting the rake ready so that he can collect a variety of small rocks near the boulder.
As a result of Jim and Dave's exploration, it is now felt that Hadley Rille was formed by flowing molten lava some 3.3 billion years ago. The lonely boulder was probably blasted out of the large crater we see beyond and to the right of the rover some 17 million years ago.