Final answer:
The lasting abandonment of Chaco Canyon was mainly due to the 300-year-long Great Drought among other factors, causing the Ancestral Puebloans to migrate and join other groups, leading to the modern Pueblo cultures such as the Hopi and Zuni.
Step-by-step explanation:
The abandonment of Chaco Canyon did not last forever, as indicated by historical and archaeological evidence. It is understood that the Ancestral Puebloans left Chaco Canyon and other significant sites like Mesa Verde due to a combination of factors including environmental changes, likely drought, resource scarcity, social strife, and external pressures from new groups moving into the area.
The most profound being the 300-year-long Great Drought that took place during a period of dramatic climatic change in North America from around 1150-1300 CE. Agricultural practices were hindered by these droughts, and with less trade and increasing reliance on new irrigation techniques, the society became more insular.
Ceremonial sites such as kivas played a substantial role in the culture, yet some evidence of deliberately set fires and closed-off structures during this period of turmoil suggests internal conflict. Eventually, the Ancestral Puebloans migrated south, joining other groups that formed modern Pueblo cultures like the Hopi and Zuni, as supported both by local oral tradition and archaeological verification.
Despite historical assumptions that the Ancestral Puebloans vanished, these migrations were part of a continuum leading to the vibrant Pueblo societies that exist today. These societies, including the Hopi, continue to maintain cultural practices such as ceremonial kiva use, as exemplified by the Hopi's Wuwuchim festival.