Final answer:
The Anasazi abandoned Pueblo Bonito and Mesa Verde due to persistent droughts, resource scarcity, and social pressures, later migrating south to join modern Pueblo cultures.
Step-by-step explanation:
The Anasazi, or Ancient Puebloans, abandoned both Pueblo Bonito and Mesa Verde primarily due to persistent droughts that spanned over the region causing shortages in food supplies and intensifying competition for scarce resources.
Archaeological evidence points to the Great Drought, which lasted from approximately 1276 to 1299 CE, as a significant factor in this migration.
The Ancient Puebloans faced additional pressures from new people moving into the area, changing agricultural practices, and possible religious turmoil, all contributing to the eventual abandonment of their cliff dwellings and communities.
Over time, the Anasazi migrated south, joining with groups that became modern Pueblo cultures like the Hopi and Zuni, as confirmed by archaeological findings and Hopi oral traditions.
The Ancient Puebloans abandoned the cliff dwellings at both Pueblo Bonito and Mesa Verde for various reasons. One significant factor was the occurrence of persistent droughts in the region, such as the Great Drought that lasted for 300 years.