The Himalaya, a classic example of a continent-continent collision zone, is tectonically subdivided into several distinct, generally east-west trending zones, separated by major thrust faults. These divisions reflect the progressive deformation and uplift resulting from the ongoing collision between the Indian and Eurasian plates. From south to north, these major tectonic zones are:

1. Sub-Himalaya (Outer Himalaya): This is the southernmost and youngest tectonic unit, comprising the Siwalik Group of rocks. It consists of molassic sediments (sandstones, siltstones, conglomerates) derived from the erosion of the rising Himalaya, deposited in foreland basins. It is bounded to the south by the Himalayan Frontal Thrust (HFT), which marks the active deformation front, and to the north by the Main Boundary Thrust (MBT).

2. Lesser Himalaya (Lower Himalaya): Lying north of the Sub-Himalaya, this zone is characterized by a thick sequence of Proterozoic to early Paleozoic sedimentary and low-grade metamorphic rocks (slates, phyllites, quartzites, limestones). These rocks are often highly folded and faulted. The Lesser Himalaya is separated from the Sub-Himalaya by the Main Boundary Thrust (MBT) and from the Great Himalaya to the north by the Main Central Thrust (MCT).

3. Great Himalaya (Higher Himalaya): This is the highest and most rugged part of the Himalaya, containing the world's highest peaks. It consists primarily of high-grade metamorphic rocks (gneisses, schists, migmatites) and crystalline granites, representing the deeply buried and metamorphosed parts of the Indian continental crust. The Great Himalaya is bounded to the south by the Main Central Thrust (MCT) and to the north by the South Tibetan Detachment System (STDS).

4. Tethyan Himalaya (Tibetan Himalaya): Located north of the Great Himalaya, this zone comprises a thick sequence of fossiliferous marine sedimentary rocks (limestones, shales, sandstones) ranging in age from Cambrian to Eocene. These rocks represent the northern passive margin of the Indian plate that was submerged under the Tethys Ocean before the collision. The Tethyan Himalaya is separated from the Great Himalaya by the South Tibetan Detachment System (STDS), a major normal fault system that accommodated extensional collapse during uplift. To its north, it is bounded by the Indus-Tsangpo Suture Zone (ITSZ).

5. Indus-Tsangpo Suture Zone (ITSZ): This is the northernmost tectonic boundary of the Indian plate, representing the actual collision zone where the Neo-Tethys Ocean closed. It is a narrow, complex zone characterized by ophiolites (fragments of oceanic crust and upper mantle), mélanges, and island arc volcanic rocks, indicating the subduction of the Tethys Ocean beneath the Eurasian plate prior to continent-continent collision. North of the ITSZ lies the Trans-Himalayan Batholith and the Karakoram-Lhasa Block, which are part of the Eurasian plate.

These tectonic subdivisions, marked by major thrust systems, illustrate the imbricate stacking of crustal slices that characterize the Himalayan orogen, each representing a distinct geological and structural history within the broader collision framework.