How does the theory of continental drift explain the formation of the himalaya mountain ranges?

Millions of years ago, the Indian Continent was an island located off the coast of Australia. When the Pangea was starting to break apart due to the continental drift, the Indian continent moved and collided with the Asian continent. The Indian continent was denser than the Asian continent and resulted in the Indian plates moving beneath the Asian plates, which pushed the less denser Asian plates upwards. This resulted to the formation of the Himalayan Mountain Ranges.

Answerdistinguish between the mercalli scale and the richter scale;