Reddit mentions of Earth: An Intimate History

Phew lets see if I can set you straight. The Himalayas were formed by continent-continet collision (i.e., India with Asia). These plates will never 'merge' although they may become sutured together. Collision zones such as these generally remain zones of weakness due to structures that form during the collision and in some cases these areas are spatially associated with rift zones if/when the plates diverge (e.g., the Appalachians mark a collisional zone but eventually rifted along the east coast). Again these concepts we are discussing are generally only applicable to continent-continent collision. When ocean plates collide with continental plates a whole different series of events is expected (see any intro geology book).

As to you second question rifting can break apart any tectonic plate. Continents are not themselves strictly the plate. These are just portions of the plate that are dominated by more buoyant crustal material. Look at a map of tectonic plates and you will notice the the continental margins don't strictly correspond to plate boundaries. Plumes do produce extensional effects however they are generally separate from regular tectonic processes. Strictly speaking rifting is caused by high heat flow and mantle convection processes. Furthermore, most plate motions are heavily influenced by dynamic mantle flow. We are just now beginning to understand in detail how differential plate motions relate to mantle flow (we've known about it for a while but many of the complexities and the importance of 3D motions are coming to light).

Long story short the Earth is one big thermo-gravitational engine. Convection in the mantle is driven by the core which in turn drives differential plate motions and related interactions. Complicated yes, but can be understood.

Hehe....hope that helps unfortunately there are a large number of concepts that go into truly 'understanding' tectonic processes and if you are just generally interested I would recommend and intro geology textbook. Or if you want a better novel style read check out this book by Richard Fortey its a great read!

http://www.amazon.com/Earth-Intimate-History-Richard-Fortey/dp/0375706208

Cheers

Earth: An Intimate History by Richard Fortey.

This book sparked my love for geology and my career.

I'd recommend about geology (http://geology.about.com/) which has a comprehensive discussion on most aspects of the subject, but geology is a subject where there is a fair amount of crossover with other subjects (which in my opinion makes it so fascinating), so you shouldn't just hem yourself into looking at straight, pure geology.

If you're willing to buy a book I'd recommend you to read http://www.amazon.com/Earth-Intimate-History-Richard-Fortey/dp/0375706208 which gives a great overview of the history of the earth.