We all got back on the bus to journey to the valley floor. Along the way, we passed a burnt-out section of forest. Apparently, a half century's worth of aggressive firefighting had resulted in a massive accumulation of underbrush, so that when the fire came, it came real hard and fast (sounds dodgy...) and was virtually unstoppable. Today, the national park ranger and firemen-type people actually set small controlled burns of the underbrush to prevent this from happening ever again. They must be the only people in world whose job is to set forests on fire.