Answer:
my guess would be neither because its just saying "cancerous" not which type but im not sure..
Explanation:
Because it causes them to move, and so they weather that way. Buut the acid rain can leak into the rock and slowly break down the atoms, causing it to chemically weather faster. Also, just regular water/rain can wash away some covering sediment.
Maybe because of global warming and the glacier water melting makING it bigger and deeper. (I hope this is the answer you are looking for)