Introduction
The Eastern Ghats constitute a discontinuous, deeply denuded chain of relict highlands extending roughly 1,750 km parallel to India's eastern littoral. Stretching across Odisha, Andhra Pradesh, Tamil Nadu, and parts of Karnataka and Telangana, they represent an exhumed Precambrian crustal belt juxtaposed against diverse bioclimatic zones.
Geological Characteristics
The Eastern Ghats represent one of the most ancient and complex tectonic provinces of the Indian shield, characterized by deep crustal processes and multi-stage metamorphism:
- Mobile Belt Evolution: The Eastern Ghats Mobile Belt (EGMB) evolved through Proterozoic collisional orogenies and terrane accretion, forming an integral suture zone linked with East Antarctica during the assembly of the Columbia, Rodinia, and Gondwana supercontinents.
- Petrology and Metamorphic Grade: The lithological assemblage is dominated by high-grade granulite-facies rocks, predominantly khondalites (garnet-sillimanite-quartz gneisses), charnockites (hypersthene-bearing granitic rocks), and massif-type anorthosites. These rocks preserve evidence of Ultra-High Temperature (UHT) metamorphism with peak conditions exceeding 900°C.
- Structural Deformation: The terrain displays intense polyphase deformation, featuring tight isoclinal folding, prominent ductile shear zones, and crustal-scale fault networks reflecting deep-seated thrusting.
Ecological Characteristics
Due to longitudinal extent and varying rain-shadow dynamics, the Eastern Ghats harbor diverse and fragmented ecosystems:
- Habitat Heterogeneity and Bioclimatic Gradient: The northern sections (such as the Maliya and Madugula ranges) receive higher precipitation and support tropical moist deciduous and semi-evergreen vegetation, whereas the southern sections (Palkonda, Velikonda, and Seshachalam hills) transition into tropical dry deciduous forests and thorn-scrub biomes.
- Biodiversity and Narrow Endemism: The region functions as a vital micro-climatic refugium hosting globally threatened and endemic taxa, including the Red Sanders (Pterocarpus santalinus), Golden Gecko (Calodactylus aureus), and Jeypore ground gecko.
- Ecological Connectivity: The Eastern Ghats establish a critical biogeographical bridge connecting with the Western Ghats at the Biligirirangana–Nilgiri node, facilitating gene flow and wildlife migration across peninsular India.
True Mountain Range or a Misnomer?
Whether the Eastern Ghats constitute a 'mountain range' requires resolving the divergence between geomorphology and structural geology:
- Physiographically a Misnomer: From a topographical and morphological perspective, the Eastern Ghats lack the continuous crestline, uniform strike, and persistent high elevation that define true mountain ranges. Extensive fluvial incision by east-flowing peninsular rivers (Mahanadi, Godavari, Krishna, and Penner) has dissected the highland into disjointed horsts, residual massifs, mesas, and monadnocks, with an average elevation hovering around 600 meters.
- Geologically Genuine: Geotectonically, the classification as a mountain belt is entirely valid. The Eastern Ghats are the deeply exhumed, root-zone remnants of a legitimate Precambrian fold-and-thrust belt that underwent substantial crustal thickening and orogenic uplift before prolonged polycyclic denudation reduced its relief.
Conclusion
While morphologically and physiographically the designation of 'mountain range' is a misnomer due to severe fluvial dissection, geologically the Eastern Ghats represent a genuine, exhumed Precambrian orogen. They are best characterized as a relict, polycyclic orogenic highland requiring conservation strategies tailored to their fragmented landscape.