The correct option is 2 and 3 only.
Explanation
The Peninsular Block is the oldest and most stable landmass of the Indian subcontinent, primarily composed of ancient gneisses and granites. It represents a rigid block that has remained largely stable since the Cambrian period, withstanding major tectonic disruptions except for limited vertical movements and block faulting.
Statement-wise Analysis:
- Statement 1 is Incorrect. The northern boundary of the Peninsular Block is not a straight line. It is an irregular line running from Kachchh along the western flank of the Aravali Range near Delhi, and then roughly parallel to the Yamuna and the Ganga as far as the Rajmahal Hills and the Ganga delta.
- Statement 2 is Correct. The Karbi Anglong and the Meghalaya Plateau in the northeast are geological extensions of the Peninsular Block. These northeastern extensions were separated from the main Chotanagpur Plateau by the Malda Fault (in West Bengal) due to tectonic movements during the formation of the Himalayas.
- Statement 3 is Correct. The Peninsular Block is characterized by relict and residual mountains, which are the remnants of older mountain systems that have been eroded over millions of years. Prominent examples include the Aravali hills, Nallamala hills, Javadi hills, Veliconda hills, Palkonda range, and Mahendragiri hills.
Key Takeaway:
The Peninsular Block is an ancient, stable landmass with an irregular northern boundary. It extends into the Northeast (Meghalaya Plateau, Karbi Anglong) separated by the Malda fault and is dominated by relict mountains and shallow valleys.