1. The Collision:
* Equal Densities: Both continental crusts have relatively low densities compared to oceanic crust. This means neither can subduct (slide under) the other.
* Immense Force: The immense pressure of the colliding plates forces the crust to buckle, fold, and uplift.
2. Mountain Building:
* Folded Mountains: The intense compression and uplift create massive mountain ranges, such as the Himalayas, the Alps, and the Appalachian Mountains.
* Faulting: The crust fractures and forms faults, creating valleys and other dramatic topographic features.
* Metamorphism: The intense heat and pressure associated with the collision metamorphose the existing rocks, transforming them into new, harder, and more resistant types.
3. Plateau Formation:
* Thickening: The collision thickens the continental crust, sometimes leading to the formation of extensive plateaus like the Tibetan Plateau.
4. Earthquakes:
* Seismic Activity: The constant pressure and movement along the fault lines result in frequent and sometimes powerful earthquakes.
5. Volcanic Activity:
* Rare but Possible: While not as common as with oceanic-continental collisions, some volcanic activity may occur due to the immense pressure melting portions of the crust.
Examples:
* Himalayas: Formed by the collision of the Indian and Eurasian plates.
* Alps: Formed by the collision of the African and Eurasian plates.
* Appalachian Mountains: Formed by the collision of the North American and African plates hundreds of millions of years ago.
In Summary:
Continental-continental collisions are powerful forces that create dramatic changes in the Earth's surface. They result in the formation of towering mountains, extensive plateaus, and significant seismic and volcanic activity. These collisions are ongoing processes that continue to shape our planet today.
