---
title: "Geology of the Terai zone"
subject: "Engineering Geology I"
chapter: 7
key: "semester_3/engineering_geology_i:geology-of-the-terai-zone"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/geology-of-the-terai-zone
site: BCT Engineering
---

# Geology of the Terai zone

Engineering Geology I · Chapter 7: Geology of Nepal

- Asked in: 2074 Asoj, 2 marks; 2068 Baisakh, 3 marks (asked 2 times)
- Video: [Shiwaliks, Duns, Bhabar & Terai Explained | Himalayan Foothills | UPSC Prelims Geography](https://www.youtube.com/watch?v=oXrvmMpFaHI) — Takshasila IAS
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/geology-of-the-terai-zone
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-7

## Question

Describe the geology (classification and lithology) of the Terai zone.

## Short answer

The Terai is divided into Bhabar (coarse gravel, boulderes, highly permeable) and Terai proper (sand, silt, clay with high water table). It consists of unconsolidated Quaternary alluvium over a thousand meters thick.

## Answer

**Terai zone.** A flat, low plain 60-300 m in altitude, the northern edge of the Indo-Gangetic plain, formed of Quaternary alluvium brought by the Himalayan rivers.

By the nature of deposits it is divided into:
1. **Bhabar zone:** a narrow belt (8-12 km wide) at the foot of the Siwalik. It consists of coarse boulders, cobbles and gravel, very permeable, so streams disappear underground.
2. **Terai proper (Terai plain):** finer sand, silt and clay with high water table and springs where the Bhabar water re-emerges.

**Lithology:** unconsolidated gravel, sand, silt and clay; thickness is over a thousand metres.

**Engineering problems:** floods and shifting rivers, high water table, liquefaction in earthquakes, low bearing capacity, and shortage of rock for aggregate.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. The Bhabar zone consists of:
   A. Fine clay with high water table
   B. Hard granite
   C. Marine limestone
   D. Coarse boulders, cobbles and gravel, very permeable, at the foot of the Siwalik
   Answer: D. Streams disappear underground there. (Key point: Bhabar)

2. In the Terai proper:
   A. Finer sand, silt and clay with high water table and springs
   B. Boulders and gravel dominate
   C. Rock outcrops everywhere
   D. The water table is very deep
   Answer: A. Bhabar water re-emerges as springs. (Key point: Terai proper)

3. Terai deposits are:
   A. Precambrian metamorphic
   B. Quaternary alluvium
   C. Miocene molasse
   D. Cretaceous marine
   Answer: B. They were brought by Himalayan rivers. (Key point: Age)

4. Which is a Terai engineering problem?
   A. Rock avalanches
   B. Permafrost
   C. Liquefaction during earthquakes and low bearing capacity
   D. Karst
   Answer: C. Floods and shortage of rock for aggregate also apply. (Key point: Problem)

## Related in Engineering Geology I

- [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×
- [Geological division of Terai and Siwalik zone](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Ageological-division-of-terai-and) — Engineering Geology I, chapter 7
- [Siwalik zone in detail](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Asiwalik-zone-in-detail) — Engineering Geology I, chapter 7, asked 2×
- [Lesser Himalaya zone in detail](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Alesser-himalaya-zone-in-detail) — Engineering Geology I, chapter 7
- [Altitude and lithology of Churiya, Fore and Trans Himalaya](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aaltitude-and-lithology-of-churiya) — Engineering Geology I, chapter 7
- [Dun valley and midland lithology and altitude](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Adun-valley-and-midland-lithology) — Engineering Geology I, chapter 7

## Related in other subjects

- [Oxidation pond for Terai town, 12,000](https://www.bctengineer.com/question.md?key=semester_6%2Fsanitary_engineering%3Aoxidation-pond-terai-12000) — Sanitary Engineering, chapter 7
- [Problems of Lesser Himalaya and Terai](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Alesser-himalaya-terai-problems) — Engineering Geology II, chapter 2, asked 5×
- [Aquifer formation in Terai and mountains](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Aaquifer-formation-terai-mountain) — Engineering Geology II, chapter 3, asked 2×
- [Engineering geological problems of Siwalik zone](https://www.bctengineer.com/question.md?key=semester_4%2Fengineering_geology_ii%3Asiwalik-problems) — Engineering Geology II, chapter 2, asked 4×