What do you mean by Geological Heritage ?

Kindly go through the chapter provided in your main course book. You can also follow the links given below to know about the threat to geological heritage, with Taj Mahal as an example:

https://www.meritnation.com/ask-answer/question/threats-to-the-geological-heritage-causes-i/unit-4-geological-heritage/6315605

https://www.meritnation.com/ask-answer/question/describe-the-threat-to-the-beauty-of-the-taj-mahal/pollution-of-air-and-water/6307476