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Mature Topography of Stable Cratons

Review Mature Topography of Stable Cratons using previous year trends.

Official Question UPSC 2026

Which of the following geographical features or phenomena is/are associated with the Peninsular Block of India ? 1. Submergence of parts of the western coast due to tectonic activity 2. Presence of residual mountain ranges such as the Veliconda hills and Mahendragiri hills 3. Deep, V-shaped river valleys formed by fast-flowing rivers Select the answer using the code given below :

Solution & Analysis

Answer: B
Let us analyze the geological structure of the Peninsular Block based on standard physical geography parameters:
•Statement 1 is Correct: Geological history shows that during the Early Tertiary period, tectonic subsidence occurred along the western flank of the rigid Peninsular block. This sinking caused the submergence of the western coastline, creating natural harbors and altering ancient drainage patterns.
•Statement 2 is Correct: The Peninsula is one of the oldest, most stable landmasses on Earth. Consequently, its mountains have faced millions of years of denudation (weathering). Today, they exist primarily as highly eroded residual or relict mountains. The Aravalis, Nallamala, Veliconda, and Mahendragiri hills are textbook examples of this topography.
•Statement 3 is Incorrect: This statement describes youthful topography. Deep gorges, rapids, and V-shaped valleys are carved by fast-flowing rivers aggressively cutting vertically through soft, young rocks—a hallmark of the Himalayan river system. Conversely, the ancient Peninsular rivers have reached maturity; they flow over hard rock with low gradients, forming broad, shallow, graded valleys.
Conclusion: Statements 1 and 2 accurately describe the Peninsular craton.

Quick Recall

The Peninsular Block of India is an ancient, stable landmass characterized by residual mountain ranges like the Veliconda and Mahendragiri hills. Historically, tectonic subsidence caused parts of its western coast to submerge. Because the landmass is ancient, its rivers have reached maturity, flowing through broad, shallow valleys rather than the deep, V-shaped gorges typical of youthful Himalayan rivers.

Concept Flow Mapping

Peninsular Block
Contains
Residual Mountains
Peninsular Rivers
Form
Broad, Shallow Valleys
Western Coast
Experienced
Tectonic Submergence

Concept Question

Geomorphologically, do the rivers of the ancient Peninsular Block form deep V-shaped valleys or broad, shallow valleys?

Key Takeaway

Broad, shallow valleys (because they are mature rivers, unlike the youthful Himalayan rivers).

Examiner's Trap

The examiner uses Statement 3 as a classic geomorphological trap. 'V-shaped valleys and fast-flowing rivers' perfectly describe the Himalayas. Candidates who fail to mentally separate the two distinct Indian geographical zones will incorrectly apply northern features to the southern plateau.

Core Insight

The Peninsular block is millions of years older than the Himalayas. Its rivers have been flowing for so long that they have already eroded the land down to its 'base level'. They no longer have the steep gradients required to engage in deep vertical erosion (cutting V-shapes); instead, they engage in lateral erosion, creating wide, mature, graded valleys.

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