An Overview on Geology, Tectonic Framework and Geo-Hazards in the Nepal Himalaya
Keywords:Nepal Himalayas, geology, tectonics, thrusts, geo-hazards, climate change
The article summarizes up-to-date information on the geology, tectonics evolution, structural setup and an overall account of the geo-hazards that frequently impact the Nepal Himalaya. The Himalayan belt terminates at the Brahmaputra River in the east and the Indus River in the west, forming syntaxial bands at both ends. Its evolution perceivably synchronised with the northward drifting Indian continent that collided with the relatively passive Eurasian continent during 40 - 55 Ma and gave rise to the Himalayan mountain range and the Tibetan plateau. The timing of collision is considered with the marine transgression of the Subathu Formation of Palaeocene to Lower Eocene age and complete withdrawal and cessation of marine sedimentation of the Tethyan basin in Post-Mid Eocene time. In this process, frontal northern margin of the Indian plate was deformed due to drastic collision and under-thrusting of the Indian craton with Lhasa block of Tibet, giving rise to north-dipping major thrusts, laterally yielding the Tibetan Tethys, Higher Himalaya, Lesser Himalaya, Sub-Himalaya and Indo- Gangetic plain. Nappe, klippe, and active faults played major role in the geo-dynamics of the Himalayan region. MCT, MBT and MFT come off together in a low-angle decollement and comprise as MHT. The cumulative effects of natural and anthropogenic hazards adversely impact the environment and ecosystems, besides causing immense economic loss.