--- title: "Physiographic division; Siwalik and Higher Himalaya" subject: "Engineering Geology I" chapter: 7 key: "semester_3/engineering_geology_i:physiographic-division-siwalik-and-higher" source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/physiographic-division-siwalik-and-higher site: BCT Engineering --- # Physiographic division; Siwalik and Higher Himalaya Engineering Geology I · Chapter 7: Geology of Nepal - Asked in: 2081 Bhadra, 5 marks - Video: [Subdivisions of Himalayas: TransHimalaya, Greater Himalaya, Lesser Himalaya, Shivalik with Animation](https://www.youtube.com/watch?v=er9fqvm1Qcs) — Zeta Axis (UPSC-SSC) - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/physiographic-division-siwalik-and-higher - Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-7 ## Question Mention the different physiographic divisions of the Himalaya. Describe the lithology and structure of the Siwaliks and Higher Himalaya. ## Short answer The physiographic divisions are Terai, Siwalik, Mahabharat, Midlands, Higher Himalaya, and Inner Himalaya. The Siwaliks are weakly consolidated Miocene-Pleistocene sandstone, mudstone, and conglomerate folded into anticlines and synclines. The Higher Himalaya consists of Precambrian high-grade gneiss, schist, migmatite and granite, with north-dipping foliation, bounded by MCT and STDS. ## Answer #### Physiographic divisions of the Himalaya | Zone | Approx. altitude | Main features | |---|---|---| | Terai plain | 60-300 m | Flat alluvial plain, Indo-Gangetic plain | | Siwalik (Churiya) range | 300-1500 m (up to 2000 m) | Youngest, low hills of weak rocks, with Dun valleys | | Mahabharat range | 1500-2700 m (up to 3000 m) | Steep, continuous ridge of the Lesser Himalaya | | Midlands (Pahad), Fore Himalaya | 800-2500 m | Hills, river valleys and basins (Kathmandu, Pokhara) | | Higher (Great) Himalaya | 4000-8848 m | Snow-capped peaks, glaciers, Mt. Everest | | Inner (Trans, Tibetan-Tethys) Himalaya | 2500-5000 m | Dry, rain-shadow region north of the Great Himalaya | **Siwalik (Churiya) zone.** The southernmost hill belt of Nepal, 10-50 km wide, altitude about 300-1500 m (up to 2000 m), lying between the MFT and MBT. Rocks are Miocene to Pleistocene molasse sediments, eroded from the rising Himalaya, mostly weak and poorly consolidated. **Lithology (three divisions)** - **Lower Siwalik:** alternation of fine-grained sandstone, mudstone and siltstone; red, purple and grey colours (Miocene). - **Middle Siwalik:** thick, massive, coarse "salt and pepper" sandstone with some mudstone and conglomerate lenses (Mio-Pliocene). - **Upper Siwalik:** poorly cemented boulder-pebble conglomerate with sandstone and clay (Plio-Pleistocene). **Structure:** the strata are folded into anticlines and synclines with strike roughly parallel to the Himalaya (WNW-ESE), often steeply dipping or overturned in the north near the MBT, and cut by thrust faults such as the MBT and MFT. **Engineering problems:** soft, erodible rocks, landslides, gullying, debris flow and flash floods. The sandstones are mostly too weak for good aggregate; the boulders and gravels of the Upper Siwalik conglomerate and of the river beds are the usual aggregate sources. **Higher (Great) Himalaya.** Lies between the MCT and STDS; altitude about 4000-8848 m. Rocks are Precambrian to Early Palaeozoic high-grade metamorphic rocks and granites. **Lithology (three formations)** - **Formation I (lower):** kyanite-sillimanite schist and gneiss, with migmatite. - **Formation II (middle):** calc-silicate gneiss, marble and diopside-bearing rocks. - **Formation III (upper):** augen gneiss, quartzite, and the Manaslu and other leucogranite intrusions. **Structure:** the Higher Himalaya is a thick slab of crystalline rocks whose foliation dips generally northward at gentle to moderate angles. It is bounded by the MCT below and the STDS above, and is folded and sheared near these boundaries. Glacial and periglacial landforms are common. **Engineering problems:** very high relief, rockfall, avalanches, glacial lake outburst floods (GLOF), glacial and moraine hazards, hard rock needing blasting, and difficult access. ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. Which description fits the Siwalik zone? A. Between MCT and STDS; high-grade metamorphic rocks B. Between MFT and MBT; weak Miocene-Pleistocene molasse sediments C. Between MBT and MCT; Precambrian slate and phyllite D. North of the Himalaya; marine limestone Answer: B. The Siwalik lies between the MFT and MBT and consists of weak, poorly consolidated Miocene to Pleistocene molasse. (Key point: Siwalik boundaries and rocks) 2. Which Siwalik division is a poorly cemented boulder-pebble conglomerate? A. Lower Siwalik B. Middle Siwalik C. Upper Siwalik D. None; all are sandstone Answer: C. Upper Siwalik (Plio-Pleistocene) is boulder-pebble conglomerate; Middle is coarse salt-and-pepper sandstone. (Key point: Siwalik lithology) 3. What are the rocks of the Higher Himalaya? A. Soft sandstone and mudstone B. Precambrian to Early Palaeozoic high-grade metamorphic rocks and granites C. Fossiliferous marine shale D. Quaternary alluvium Answer: B. The Higher Himalaya has high-grade metamorphics (schist, gneiss, migmatite) and leucogranite intrusions. (Key point: Higher Himalaya lithology) 4. Which engineering problem is typical of the Higher Himalaya but not of the Siwalik? A. Gullying and debris flow in soft rock B. Glacial lake outburst floods and avalanches C. Poor consolidation D. Flash floods from soft hills Answer: B. Higher Himalaya hazards include very high relief, rockfall, avalanche and GLOF; Siwalik problems come from soft, erodible rock. (Key point: Engineering problems) ## Related in Engineering Geology I - [Discontinuities; Siwalik and Higher Himalaya lithology](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Adiscontinuities-siwalik-and-higher-himalaya) — Engineering Geology I, chapter 7 - [Physiographic division of the Nepal Himalaya](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aphysiographic-division-of-the-nepal) — Engineering Geology I, chapter 7, asked 7× - [Lithology of Lesser and Tethys Himalaya; Siwalik difference](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Alithology-of-lesser-and-tethys) — Engineering Geology I, chapter 7 - [Lithology of Higher Himalaya and Tethys zone](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Alithology-of-higher-himalaya-and) — Engineering Geology I, chapter 7, asked 3× - [Physiographic and tectonic division of Nepal](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aphysiographic-and-tectonic-division-of) — Engineering Geology I, chapter 7 - [Tectonic divisions of the Nepal Himalaya](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Atectonic-divisions-of-the-nepal) — Engineering Geology I, chapter 7, asked 4× ## Related in other subjects - [Problems of Siwalik and Higher Himalaya](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Asiwalik-higher-himalaya-problems) — Engineering Geology II, chapter 2, asked 2× - [Problems of Higher and Tethys Himalaya](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Ahigher-tethys-problems) — Engineering Geology II, chapter 2 - [Geological hazards of Higher Himalaya](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Ahigher-himalaya-hazards) — Engineering Geology II, chapter 2