What mishap occurs shortly after the man eats lunch and resumes his journey?

In a seemingly safe, solid spot, the man falls through the snow and wets himself up to his shins. He curses his luck; starting a fire and drying his foot-gear will delay him at least an hour. He gathers brush and builds a fire, aware that his numb feet must not remain wet. His exposed fingers (necessary to make the fire) are also numb, and having stopped walking, his heart no longer pumps warming blood as much throughout his body. But the fire builds up, and the man feels safe. He remembers the old-timer from Sulphur Creek who had warned him that no man should travel in the Klondike alone when the temperature was fifty degrees below zero. He thinks the old-timers are "womanish," and that even with his "accident," he had saved himself in solitude. Nevertheless, it is extremely cold, and his fingers are almost completely numb.

The man unties his icy moccasins, but before he can cut the frozen strings on them, clumps of snow from the spruce tree above fall down and snuff out the fire. Though building a fire in the open would have been wiser, it had been easier for the man to take twigs from the spruce tree and drop them directly below on to the fire. Each time he pulled a twig, he had slightly agitated the tree until, at this point, a bough high up had capsized its load of snow. It capsized lower boughs in turn until a small avalanche had blotted out the fire.