What is the physics behind being able to land unharmed on a slope from a high height? (i.e. snowboard, dirtbik?

There's probably a better way to word the question. we all have this as "physics logic" in our heads, but what is the physics behind this? Also, I'm doing this as part of a p.o.i. (point of interest) project on the physics of snowboarding... any other help on this would be appreciated!