The enormous wall of mountain ridges, with the Himalayas as the highest in the world, separates South Asia, the subcontinent of India, from the rest of Asia. This ''mountain wall'' came to existence when India, once a separate huge island, moved in and collided with the Eurasian tectonic plate. Both of then had the same crust density, so their collision made the crust lift upwards under the pressure and in time create this huge ''mountain wall''. The process of the mountains getting higher continues to this day, and is estimated that they grow 8 cm per year in height.