Final answer:
The Anasazi, or Ancient Puebloans, declined due to a combination of factors including the Great Drought and possible religious turmoil, before ultimately migrating south and integrating into what became modern Pueblo cultures.
Step-by-step explanation:
End of Anasazi Civilization
The end of the Anasazi, known as Ancient Puebloans, does not have a clear-cut reason. This civilization, which flourished in the Four Corners area (Colorado, Utah, Arizona, and New Mexico), underwent significant changes around 1150-1300 CE.
Factors contributing to their decline include the Great Drought, a period of dramatic climatic change that lasted for 300 years.
The Anasazi became more insular, reduced trade, and intensified agriculture with new irrigation techniques. In addition, there were signs of religious turmoil, and evidence of fires and boarded-up structures at several ceremonial sites.
Although many towns were abandoned by 1300 CE, it is commonly believed that the Anasazi migrated south to join groups that eventually became modern Pueblo cultures like the Hopi and Zuni, which is supported by archaeological evidence.