One very good example of cause-and-effect in "To Build a Fire" is the protagonist's lack of preparation. He receives explicit advice from an experienced man who has traveled the Yukon for years:
That man from Sulphur Creek had spoken the truth when telling how cold it sometimes got in the country. And he had laughed at him at the time!
The old-timer had been very serious in laying down the law that no man must travel alone in the Klondike after fifty below.
(London, "To Build a Fire," eNotes eText)
His laugh at the admonition to travel with a companion and prepare for bitter cold shows his ego, and his belief that he is able to conquer nature with little more than his personal willpower. However, he is quickly damaged by the cold, falling into a spring which wets his clothing -- this is practically a death-sentence in the Yukon. As he tries to light a fire, his freezing hands refuse to work; with a companion, he could have survived. Ignoring the advice of a wiser man directly leads to his death.