Floods ripped through rock formations (8)
I believe the answer is:
torrents
'floods' is the definition.
(I've seen this before)
'ripped through rock formations' is the wordplay.
'ripped' becomes 'rent' (synonyms).
'through' indicates putting letters inside (inserted letters go through the word).
'rock formations' becomes 'tors' (I can't explain this - if you can you should give a lot more credence to this answer).
'rent' put within 'tors' is 'TORRENTS'.
Can you help me to learn more?
(Other definitions for torrents that I've seen before include "Floods" , "Violently fast streams of water" , "Fast streams of liquid" , "Cats and dogs" , "Cascades of water" .)