In Into Thin Air, what do the climbers find scattered all over the ground at Camp Four?

The book Into Thin Air tells of the harrowing experience of a group of climbers who attempt to summit Mount Everest. Most of the group succeeds—some do not.

When the climbers reach Camp Four during their ascent to the top of the mountain, they stumble upon more than 1,000 empty oxygen canisters strewn about the ground. The group learns that the canisters are being brought back down the mountain by sherpas. The sherpas are paid a cash bonus for each canister they bring back down the mountain.

The book's author—Jon Krakauer—seemed to suggest that there was more space for canisters than tents at Camp Four when he writes "the tents of Camp Four squatted on a patch of barren ground surrounded by more than a thousand discarded oxygen canisters."

It has been estimated that there are nearly 10 tons of trash left on Mount Everest. Some groups now climb Everest with the specific purpose of cleaning the mess made there.