What are the craters on the moon with peaks in the middle of them? Was taking some extremely amatuer pictures of the moon from my cheap telescope with my camera phone...



You see the crater Im talking about? Top right.The one with a little nub in the middle- which Im sure is actually massive. How was this formed differently than the other craters? What couldve caused the hill?
Nice picture! Those peaks are actually a very common feature in craters formed by large impacts. Craters with these features are known as "complex craters". Basically what happens is that when the meteor hits, it pushes in the surface. Then the underlying mantle produces an "elastic rebound" and pushes outwards. This is a similar effect to what happens when you hit a drum. Your drumstick rebounds off the drum, and the drum begins to vibrate. Since rock (even molten rock) is much more dense than a drumskin, it does not vibrate very much. The vibrations solidify, resulting in a crater with one central peak.

How exactly this happens is still being investigated. This paper provides a pretty good explanation of what happens, but it's quite technical.



Even larger impacts will produce ring structures. These are relatively rare on the Earth, since such structures are quickly weathered away. A good example of this is the Chicxulub crater off the Yucatan peninsula (the impact that killed the dinosaurs).