Scree slope leading to an extremely high over vertical dropoff at the top of a mountain. Slipped, started sliding and couldn't scrabble faster than the loose rocks flowed.

There was one single small scraggly shrublet. It had a single root that after previous rock slides had been exposed for a good foot.

I scrabbled sideways and managed to get one hand onto the root just as my feet were going off the edge. The root creaked and for an eternity I thought it would break. It did not.

I pulled my legs back up and managed to scrabble the fuck back up. Worst school excursion ever.