Diastrophism refers to the large-scale deformation of the Earth’s crust due to tectonic forces. It encompasses folding, faulting, and warping, which create mountains, plateaus, rift valleys, and basins. These processes are driven by compressional, tensional, and shear stresses generated by mantle convection, plate movements, and isostatic adjustments.
Folding occurs when compressional forces bend rock layers without breaking them. This creates anticlines (upward folds) and synclines (downward folds). The Himalayan mountain range, formed by the collision of the Indian and Eurasian plates, is a classic example of folding. The Alpine-Himalayan belt is a global hotspot for folded mountains, which influence regional climates, river systems, and biodiversity. In India, the Aravalli Range, one of the world’s oldest fold mountains, exemplifies ancient folding activity.
Faulting involves the fracture and displacement of rock layers along a plane, known as a fault. Faults are classified into normal faults (tensional stress), reverse faults (compressional stress), and strike-slip faults (shear stress). The San Andreas Fault in California is a well-known strike-slip fault. In India, the Narmada-Son Lineament, a major tectonic fault line, has shaped the Vindhya and Satpura ranges and is associated with seismic activity. The Bhuj earthquake of 2001 was linked to reactivated faults in the Kutch region.
Warping refers to broad, gentle bending of the crust over extensive areas, often due to isostatic adjustments or magma movement. The Deccan Plateau in India, formed by volcanic activity and subsequent uplift, demonstrates warping. Similarly, the Gangetic Plains have undergone subsidence due to sediment load, creating a trough that hosts one of the world’s most fertile alluvial basins.