People rock crawl up a steep obstacle.
A group of people climb a mountain.
The people rock-crawling don't necessarily have to be united as a group.  Something does not have to be a mountain to be a steep obstacle.
exists s1 x1 x2 x3 x4.(a_topic(x1) & up(x1,x4) & n_obstacle(x4) & a_steep(s1) & Theme(s1,x4) & n_crawl(x1) & of(x1,x3) & n_rock(x3) & of(x1,x2) & n_people(x2))
exists e1 x1 x2 x3.(Theme(e1,x3) & Actor(e1,x1) & v_climb(e1) & n_mountain(x3) & of(x1,x2) & n_people(x2) & n_group(x1))