The correct option is (a).
Explanation
The physiography of India is defined by three distinct geological units: the ancient and stable Peninsular Block, the young and geologically active Himalayas, and the recently formed Indo-Ganga-Brahmaputra Plains.
Statement-wise Analysis:
- Statement 1 is Correct: The Peninsular Plateau is a part of the ancient Gondwanaland. It was formed due to the breaking and drifting of the Gondwana landmass. Geologically, it constitutes one of the most ancient and stable landmasses on the earth’s surface, composed primarily of old crystalline, igneous, and metamorphic rocks.
- Statement 2 is Incorrect: The Himalayas and the Northern Plains are the most recent landforms, not the oldest. The Himalayas are young fold mountains formed during the Tertiary period. The Northern Plains are even younger, formed by alluvial deposits in the foredeep created south of the rising Himalayas.
- Statement 3 is Incorrect: From a geological viewpoint, the Himalayan mountains form an unstable zone. Being young fold mountains located at the convergent boundary of tectonic plates, they exhibit youthful topography (high peaks, deep valleys, fast-flowing rivers) and are prone to high seismic activity.
Key Takeaway:
The Peninsular Plateau represents an ancient, stable shield area, whereas the Himalayas are geologically young, unstable, and tectonically active fold mountains.