MISSING LINKS AND DAWN MONKEYS

To the north and east, wheat fields extend across the plateau as far as
the eye can see. Immediately west of the ravine, the sleepy village of Zhaili
shelters the peasant farmers who tend the surrounding fields. A narrow
path, hewn into the western wall of the ravine, provides access to the
bottom some 150 feet below for the villagers and their sheep and goats.
Walking down this path, you can’t help but notice the peculiar nature of
the nearly vertical walls of the ravine. The rock defining both sides of
the ravine is soft and pliable, so easy to work that many people in this
part of China actually carve small caves into it, which function as storage
rooms or even small homes. Geologically, this type of rock is known
as loess. It is composed of wind-blown sediment laid down by countless
dust storms that swept across this part of China during the Pleistocene
Epoch, when vast ice sheets were expanding and contracting farther north
in Siberia.