One of the most distinguishing features of Tibet obviously, are the Himalaya Mountains along its southern border.
These feats of plate tectonics were the result of the Indo- Australian plate colliding with the Eurasian plate about seventy million years ago. (thinkquest.com Formation of the Himalayas) Before this time, there was a sea that occupied the area between the plates where the mountains are now located known as the Tethys. As the super continent Pangea began to break up, this ocean was filled with the sediments of rivers from the Indian and Eurasian landmasses. (thinkquest.com Formation of the Himalayas) The crust of the Indian Plate was being subducted underneath the Asian Plate, which pulled the Indian Plate towards the Asian, which caused a collision and thrust the Eurasian plate on top of the Indian Plate creating the Himalayas.
Mt. Everest, the tallest of the Himalaya, is made up of sedimentary rock, or a combination of the eroded rock from the Eurasian and Indian rivers long before, which adds to proof that it was once underwater as suggested above. It is possible also, to see the Strata, or layers of rock on Everest as well, which create lines across its face and are visual portrayals of the different time periods and sediment collection. Everest is different from much of the rest of the Himalaya, the primary make up of Tibet is Limestone and Sandstone, sedimentary rock, but the Himalaya are made up of gneiss and schist, metamorphic rock, which is due to the intense pressure and heat when the mountains were created. (Mountains of Tibet factsanddetails.com)
Not only did the collision of the two plates create the modern Himalaya, it also created what is now called the Tibetan Plateau. This is the largest and highest place in the world. (Geology/about.com The Tibetan Plateau) The Plateau is a mix of continental fragments, which would suggest that most of the rocks that can be found on and in the Plateau would be sedimentary. (Geology of the Tibetan Plateau http://oak.ucc.nau.edu)
