Question

What caused the decline of the people at Chaco Canyon?

Answer 1

Both drought and human activity contributed to environmental changes which led to the decline of the culture at Chaco Canyon

Answer 2

But by the end of the 12th century, Chaco Canyon had been abandoned. No one knows why for sure, but the thinking among archaeologists has been that excessive logging for firewood and construction caused deforestation, which caused erosion, which made the land unable to sustain a large population.