Q1. (a) What are truncated spurs’? Where and how are they formed?  10 Marks (PYQ/2024)

Answer:

Geomorphology  – Glacial landforms

Introduction

Truncated spurs are steep, cliff-like edges of interlocking spurs that have been sharply cut off by the erosive action of valley glaciers. They are classic features of glacial troughs and represent significant landscape modification by glacial geomorphological processes.

Concept and Definition

A spur is a lateral ridge projecting into a valley, typically formed by fluvial erosion where rivers meander around resistant rock outcrops. In river valleys, they form interlocking spurs. However, glaciers, being more powerful agents of erosion due to their sheer mass and movement, tend to truncate these spurs as they move through a valley.

Definition: A truncated spur is a steep, blunt-ended ridge that results from the erosional truncation of an interlocking spur by a glacier.

Formation Process

1. Glacial Erosion

• Dominated by abrasion (rock scraping) and plucking (removal of bedrock).
• Unlike rivers, glaciers move straight through valleys, cutting across the interlocking spurs instead of meandering.
• Over time, glaciers smoothen and straighten the valley, leaving behind steep-sided spurs.

2. Post-Glacial Modification

• These spurs remain as sharp cliffs rising above the U-shaped valley formed by the glacier.

Geographical Distribution & Examples

• Lake District (UK) – e.g., the Langdale Valley.
• Alps – Numerous glacial valleys show such features.
• Karakoram and Himalayas – Higher altitudes exhibit similar glacial erosion forms.

Theoretical Perspectives

• Davis’ Cycle of Erosion: Although primarily fluvial, it highlights stages of landscape evolution; glaciers represent a rejuvenating agent modifying the mature fluvial landscape.
• Penck’s Slope Replacement Theory: Spurs are modified by parallel retreat, applicable when post-glacial weathering continues the modification of spurs.
• Quantitative Revolution: Modern geomorphologists use GIS and DEMs to study spur truncation and glacier dynamics.

Conclusion

Truncated spurs are vital indicators of past glacial activity, illustrating how glacial geomorphic processes reshape fluvial landforms. Their formation is a testament to the power of ice as a geomorphic agent and helps reconstruct paleoclimatic and paleogeographic conditions.