---
title: "Short note: Mountain system"
subject: "Engineering Geology I"
chapter: 2
key: "semester_3/engineering_geology_i:short-note-mountain-system"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/short-note-mountain-system
site: BCT Engineering
---

# Short note: Mountain system

Engineering Geology I · Chapter 2: Basic Reviews of the Earth

- Asked in: 2063 Baisakh (old course), 2 marks; 2062 Baisakh (old course), 2 marks (asked 2 times)
- Video: [Himalaya's Fold mountains and Thrust boundaries explained with animation (part 2/3) | UPSC](https://www.youtube.com/watch?v=mF58L2J0FK4) — 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/short-note-mountain-system
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-2

## Question

Write a short note on mountain systems (folded mountains).

## Answer

A **mountain system** is a group of mountain ranges related in origin, age and structure, forming a long belt, for example the Alpine-Himalayan system.

#### Fold mountains
- Formed when sediments deposited in a long, sinking basin (geosyncline) are compressed by plate collision, causing them to fold, fault and rise.
- Characterised by long, narrow belts of folds (anticlines and synclines), thrust faults, metamorphism and igneous intrusions.
- Young fold mountains: Himalaya, Alps, Andes, Rockies. Old ones: Appalachians, Aravalli.

```text
   /\    /\    /\      anticlines
  /  \  /  \  /  \
 /    \/    \/    \    synclines
```

#### Importance
- They contain the source areas of major rivers, mineral deposits and hydropower sites.
- They are tectonically active, with earthquakes and landslides, so they need careful engineering geological study.

## Check yourself

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

1. Fold mountains form when:
   A. Sediments in a sinking basin are compressed by plate collision
   B. Plates diverge
   C. Volcanoes erupt
   D. Rivers deposit sand
   Answer: A. Compression folds and uplifts. (Key point: Formation)

2. Which is a young fold mountain?
   A. Appalachians
   B. Himalaya
   C. Aravalli
   D. Black Forest
   Answer: B. Appalachians and Aravalli are old. (Key point: Young belts)

3. Why do mountain belts need careful study?
   A. They are inert
   B. They have no rivers
   C. They are tectonically active with earthquakes and landslides
   D. They have no rocks
   Answer: C. Active tectonics causes hazards. (Key point: Engineering importance)

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