It is true that Indus Valley Civilization exists in what is now 'Pakistan' for about '1000' years ago.
<u>Explanation:</u>
Commercial, religious, artistic connections have been existing then. The life was 'highly developed' city life with wells, bathrooms, drainage system etc.
It is believed that the "drying of the River Saraswathi " was the main reason for the decline of the 'Indus Valley civilization'.
Floods in the area was also another cause of concern. This made the economy no longer sustainable.
From my understanding of what i learned from middle school a volcano erupts when it creates enough lava to explode for example if you had a balloon that you were inflating too much eventually it will explode