The Indus Valley civilization of ancient India

Winter monsoons brings dry, hot air that can damage and destroy crops. The summer monsoon brings wet, heavy rains that are necessary for crop growth, but that also have the potential to cause flooding, which can lead to famine. Geologist Anil Gupta of IIT Kharagpur has studied the effect of monsoons over the past 10,000 years, and he has concluded that a strong monsoon helped in the growth of civlization, whereas, a weakening monsoon possibly contributed to its decline.

The Arabian Sea sediments and other geological studies show that the monsoon began to weaken about 5,000 years ago. The dry spell, lasting several hundred years, might have led people to abandon the Indus cities and move eastward into the Gangetic plain, which has been an area of higher rainfall than the northwestern part of the subcontinent.

“It’s not high temperatures, but lack of water that drove the people eastward and southward,” Gupta said. About 1,700 years ago, the monsoon began to improve again, leading to increased farm produce for several centuries and contributing to the relative prosperity in India during the medieval ages, from AD 700 to 1200. [Indus cities dried up with monsoon].