QuoteAnd nothing on the derelict seems to be in good shape and by the time of ALIENS it's even breaking apart.
Cameron needed an excuse as to why the derelict's warning beacon was no longer transmitting so he came up with the idea of a lava flow having damaged the derelict in the timeframe between Alien and Aliens. He probably wasn't aware at the time that in the original Alien storyboard Dallas had switched it off.
With regards to Prometheus - there is some very heavy erosion on that pyramid/dome structure. The head sculpture is almost completely eroded which gives you an indication of the severity of the weather on LV-223. But then again, the same could be said for the Sphinx on earth and a collision with a starship barely scratched the Juggernaut's paint job.