Which of the following major physiographic divisions of India is geologically the oldest landmass?

Introduction / Context:
This question tests your understanding of the geological history of India major landforms. The country is divided into several physiographic divisions such as the Himalayan mountains, the plains and the Peninsular Plateau. Identifying which of these is geologically the oldest helps you understand how the Indian landmass evolved over time.

Given Data / Assumptions:

• The options include the Himalayan Mountain Chain, the Indus Ganga Brahmaputra plain, the Peninsular Plateau, the Coastal Plains and the Thar Desert.
• The question asks for the geologically oldest of these divisions.
• We assume the standard geological narrative that places the Indian shield as very ancient compared to younger mountain ranges and plains.

Concept / Approach:
The Peninsular Plateau, also called the Indian shield or the Deccan Plateau region, consists of very old crystalline and metamorphic rocks that date back to Precambrian times. It is geologically stable and has not been significantly affected by recent orogenic movements. In contrast, the Himalayan Mountain Chain was formed much later due to the collision of the Indian and Eurasian plates. The northern plains and coastal plains are even younger, formed by river and marine deposits. Therefore, the Peninsular Plateau is regarded as the oldest physiographic division.

Step-by-Step Solution:
Step 1: Recall that the Peninsular Plateau is often described as a stable block of very ancient rocks forming the core of the Indian landmass. Step 2: Recognise that the Himalayas are relatively young fold mountains formed in the geologically recent Cenozoic era. Step 3: Understand that the Indus Ganga Brahmaputra plain is composed of alluvial deposits laid down by rivers in recent geological times. Step 4: Note that coastal plains and the Thar Desert are also products of more recent depositional and erosional processes. Step 5: Conclude that the Peninsular Plateau is the oldest among the listed physiographic features and select it as the answer.

Verification / Alternative check:
Verification is straightforward if you consult any school geography textbook or basic geology reference. They clearly state that the Peninsula of India forms part of one of the oldest landmasses on earth, with rocks that are several hundred million years old. They also describe the Himalayas as young fold mountains and the northern plains as recent alluvial formations, which confirms that the Peninsular Plateau is geologically the oldest division.

Why Other Options Are Wrong:
The Himalayan Mountain Chain is younger than the Peninsular Plateau and continues to be geologically active due to ongoing plate convergence. The Indus Ganga Brahmaputra plain is formed by river deposits over the last few million years and is therefore much younger. The Coastal Plains are narrow strips of land along the seaboard formed by marine and fluvial deposition, also relatively recent. The Thar Desert is a landscape shaped by wind erosion and deposition in more recent geological times and does not predate the ancient shield rocks of the Peninsular Plateau.

Common Pitfalls:
Students sometimes mistakenly focus on the size or prominence of a feature rather than its geological age and choose the Himalayas because they dominate the northern skyline. Others may not distinguish between erosional age of a landscape and the age of the underlying rocks. To avoid such mistakes, remember that the Peninsular Plateau is the ancient core of the Indian landmass, while the Himalayas and plains are much more recent additions.

Final Answer:
The Peninsular Plateau