Let's understand how heavy rainfall can cause a landslide in a hilly area: --- 1. Imagine a steep hill in the Himalayas. The soil on this hill is usually held together by tree roots. --- 2. Now, heavy monsoon rains start falling continuously for several days. The rainwater seeps deep into the soil. --- 3. The soil becomes completely saturated with water, making it very heavy and loose. The water also acts like a lubricant, reducing the friction that holds the soil to the bedrock. --- 4. The added weight of the water and the reduced friction make the soil unstable. The force of gravity pulling the heavy, wet soil downwards becomes stronger than the forces holding it in place. --- 5. Suddenly, a large section of the waterlogged soil and rocks breaks away from the hillside and slides rapidly downwards. This is the landslide. --- 6. This landslide can block roads, damage houses, and carry away anything in its path, just like we see during heavy rains in places like Uttarakhand or Himachal Pradesh. --- Answer: Heavy rainfall saturates soil, making it heavy and loose, which gravity then pulls down as a landslide.