Rocks spark questions

On Friday we went for our first community walk of the year.
What happened here?

On Friday we went for our first community walk of the year.  It was a beautiful fall day, amazingly warm for September. We hiked up through one of our neighbourhood green spaces.  I think it’s been saved from development because of its geography.  The path runs between two rock cliffs.  As we walked, I asked the children how the rocks got split in half.  Theories ranged from “It was an avalanche Madame.” “I think there was an earthquake.”  “It was the wind.” “Water did it.”

So… how did the rocks get like this?  I’ll give you a hint.  It also made the scratches on these rocks which you can find in our other nearby greenspace.

What made these?
What made these?

Any guesses?