Correct Option
The correct option is Heavy rainfall from the South West Monsoon.
Explanation
The Meghalaya Plateau (also known as the Shillong Plateau) is a geological extension of the Indian Peninsular Plateau, separated by the Malda Gap. Despite its geological stability, the surface of the plateau is highly degraded and eroded due to exogenic forces, specifically the climatic conditions prevalent in the region.
Detailed Analysis
- Glacial activity in the past is Incorrect: Glacial activity is characteristic of high-altitude regions or high-latitude zones. The Meghalaya Plateau, located in a tropical/sub-tropical zone with moderate elevation, has not experienced significant glacial activity in the recent geological past.
- Heavy rainfall from the South West Monsoon is Correct: The plateau receives the highest rainfall in the world (e.g., Mawsynram and Cherrapunji) due to the funnel-shaped arrangement of the Garo, Khasi, and Jaintia hills, which trap the moisture-laden South West Monsoon winds. This intense and continuous precipitation leads to severe sheet and gully erosion, stripping away the topsoil and resulting in a highly eroded, rocky surface.
- Frequent tectonic movements is Incorrect: While the region is seismically active and tectonic movements have shaped the plateau's elevation and the faulting of the Malda Gap, the eroded surface texture is a result of denudation agents (water) rather than tectonic uplift or subsidence.
- Wind erosion similar to the Indian Desert is Incorrect: Wind erosion is the dominant geomorphic agent in arid and semi-arid regions with loose soil and little vegetation, such as the Indian Desert (Thar). The Meghalaya Plateau is a humid region with dense vegetation in parts, making water the primary agent of erosion, not wind.
Key Takeaway
The Meghalaya Plateau is a highly eroded surface primarily due to the extreme precipitation received from the South West Monsoon, which acts as a powerful agent of denudation on this extension of the Peninsular block.