Final answer:
The Indus Valley Civilization declined due to environmental factors, invasion by outside forces, and economic decline.
Step-by-step explanation:
The decline of the Indus Valley Civilization is believed to have been caused by a combination of factors:
- Environmental factors: Environmental degradation due to resource exploitation, high population density, climate change, and disease likely played a role in the civilization's decline.
- Invasion by outside forces: The civilization was vulnerable to attacks by raiding groups like the Aryans, who likely took advantage of the weakened state of the region.
- Economic decline: Centuries of urbanization and population growth may have led to environmental degradation, making the land unsuitable for sustaining human populations.