I had a question concerning the nature of continental plates.
When looking at the Eurasian Plate today, for the most part, there is one solid fragment of the Earth's crust. However, having had a look at maps detailing prehistoric Earth, this isn't always the case. Throughout the entire Phanerozoic Eon, Eurasia has been a collection of different landmasses gradually merging together. Baltica, Kazakhstania, all the various regions of East and South-East Asia. Yet, today, only India and Arabia are still situated upon separate plates. All others no longer possess any divisions between them.
Why is this the case? I was under the assumption that it was only oceanic plates that submerge into the mantle due their density. I though that when continental plates collide, neither continent submerges, forming mountains. Shouldn't there still be distinct tectonic plates?
Any answers would be greatly appreciated.