Along that shadow line, you’ll see mountaintops protruding high enough to catch sunlight, while dark, low-lying terrain surrounds them. On large crater floors, you can follow “wall shadows” cast by the sides of craters hundreds or thousands of feet high. What’s more, these features change in real time, and you can see striking differences in just one night.
Two-part landscape
Scientists differentiate features on the Moon between lighter areas, called highlands, and darker features, called maria (the Latin word for seas). The dark material inside maria is solidified lava, and it dates back to periods of volcanism that ended about a billion years after the Moon formed (which happened some 4.5 billion years ago).
But the lava isn’t even the oldest part of the Moon. That honor goes to the highlands, which consist of ancient lunar surface rock and materials thrown out during previous explosive impacts. The highlands are a Moon watcher’s treasure-trove of mountains, valleys, bright areas, and shadows.