When two continental plates collide neither plate can be subducted due to their high bouyancy . ... After collision the oceanic lithosphere breaks off and sinks into the mantle. The subduction zone eventually becomes inactive The two continents become welded together as they are compressed together over time.
Explanation:
A subduction zone is the biggest crash scene on Earth. These boundaries mark the collision between two of the planet's tectonic plates. The plates are pieces of crust that slowly move across the planet's surface over millions of years.
Where two tectonic plates meet at a subduction zone, one bends and slides underneath the other, curving down into the mantle. (The mantle is the hotter layer under the crust.)
Tectonic plates can transport both continental crust and oceanic crust, or they may be made of only one kind of crust. Oceanic crust is denser than continental crust. At a subduction zone, the oceanic crust usually sinks into the mantle beneath lighter continental crust. (Sometimes, oceanic crust may grow so old and that dense that it collapses and spontaneously forms a subduction zone, scientists think.)
If the same kind of crust collides, such as continent-continent, the plates may crash together without subducting and crumple together like crashing cars. The massive Himalaya mountain chain was created this way, when India slammed into Asia.
