Along the Karakorum Highway you can observe different geomorphologic structures and different types of rocks. There are mainly metamorphic, meta igneous volcanic and some sedimentary rocks. The geology of Kohistan is different and unique in the area, containing mafic and calalkaline types of rocks. Kohistan constitute about 36000 sq. kilometers of the territory located between Indo-Pakistan and Eurasian plates, on the north western side of the Himalayas. This part is known as the tectonic zone of Karakoram. The area of Gilgit and Baltistan are mostly over lying by sedimentary rocks of younger age. There are large and small outcrops of intrusive acidic, intermediate and ultramafic rocks. In the eastern part near Chilas and Besham the ultramafic rocks
exposed. Bulk of kohistan sequence consists of Amphibolites, Diorites and associated volcanic rocks. Structural observations show that due to collision of two plates, Hindu Kush, Himalayas, Karakorum and
other mountains were built different structures shows the subduction and also obduction of two plates. The oceanic plate is heavier than the continental plate so, oceanic plate sub-ducted under the continental plate. Geologically there are three main parts of region, Indian Plate or Indian Mass, Asian Plate or Asian Mass and Kohistan sequence. In Swat Valley this suture is represented by talc carbonate schist, which is the host for gem quality emeralds. In Kohistan the basement is represented by deep crystal and upper mantle rock (ultramafics and garnet granulites) of Jijal complex, followed by meta volcanic of Komila amphibolites belt, and the Chilas complex (layered intrusion consisting of gabbros (Norited, Choromitites and ultramfics). Volcanic arc of Kohistan is represented by Chalt volcanic, which is overlain by marine sediments of Yasin Group.
The MKT, Main Karakuram Thrust that is the collision of the Indo-Pak and the Eurasian plate located at the Chalt-Nagar Valley. The history of tectonic evolution has very close relationship with different period of organic movement caused by under thrust of IndoPakistan (Indian) plate, north below the Eurasian Plate. Geologically millions of years ago, now the Northern Areas of Pakistan were submerged under a sea called “Tethyn” between Indo-Pak and Eurasian plate. During this collision Indo-Pak plate sub-ducted under the Eurasian plate, which is still going on, about 5cm per year. During this organic movement Tethyn Sea disappeared and reduced to now Arabian Sea when plates became closed. The remained material of the sea and newly erupted material by lava formed two Island arcs,
Kohistan Island arc (Jajil to Chalt) and Ladhk Island arc (some parts of Baltistan is on Ladhk Island arc). Both plates have now continental parts. Due to this continental collision raise of Karakorum and Himalayas took place, which are highest as well as youngest mountain ranges in the world. Indo-Pak plate is still sub-ducting under the Eurasian plate. The mountain chain being squeezed upward as the Indo-Pak plate pushes against the Eurasian plate. The mountains are rising at an average rate of 7mm per year. Actually the mountains are raising highly due to this effect the rate of denudation is also high. In this way canyons and gorges become deeper and deeper.