Peninsular Hills of India

Introduction

The Peninsular Hills form an integral part of the Peninsular Plateau, one of the oldest and most stable landmasses in India. These hills are characterized by their geological antiquity, diverse formations, and significant influence on the region’s topography, climate, and biodiversity. 

Overview of the Peninsular Plateau

• The Peninsular Plateau is roughly triangular in shape, with its broad base at the southern edge of the Indo-Gangetic Plains, tapering down to Kanyakumari at the southern tip of India.
• It covers an area of about 16 lakh square kilometers, almost half of India’s total land area, making it the largest physiographic unit in the country.
• The plateau is a stable geological shield composed predominantly of ancient igneous and metamorphic rocks such as granites, gneisses, schists, and sedimentary formations from the Vindhyan and Gondwana periods.
• It slopes generally from west to east, which influences the flow direction of most peninsular rivers draining into the Bay of Bengal, except for a few like the Narmada and Tapi which flow westward.

Major Hill Ranges of the Peninsular Plateau

The Peninsular Hills are made up of several prominent mountain and hill ranges that surround and dissect the plateau. These include:

1. Aravali Hills

• One of the oldest mountain ranges in the world, extending from Gujarat through Rajasthan to Delhi.
• These hills are highly eroded and appear as broken or residual hills.
• They form the northwestern boundary of the Peninsular Plateau and separate it from the Indo-Gangetic plains.

1. Vindhya Range

• Located south of the Indo-Gangetic plains, running east-west.
• Acts as a natural boundary between northern India and the peninsular region.
• Composed mainly of sedimentary rocks like sandstone, shales, and limestones from the Vindhyan period.
• The Vindhya range is significant in dividing the northern plains from the peninsular plateau.

1. Satpura Range

• Situated south of the Vindhyas, running east-west.
• Characterized by a series of scarped plateaus with elevations ranging between 600 to 900 meters.
• It forms the northern boundary of the Deccan Plateau and is known for its dense forests and biodiversity.

1. Western Ghats (Sahyadris)

• Runs parallel to the western coast of India.
• Higher and more continuous than the Eastern Ghats, with average elevations around 1,500 meters.
• Home to the highest peak of the Peninsular Plateau, Anaimudi (2,695 m) in the Anaimalai Hills.
• Origin of many peninsular rivers such as the Godavari, Krishna, and Cauvery.
• Ecologically significant with rich biodiversity and numerous endemic species.

1. Eastern Ghats

• Discontinuous and lower in elevation compared to the Western Ghats.
• Stretches along the eastern coast from Odisha to Tamil Nadu.
• Composed of ancient rock formations, heavily eroded by rivers like the Mahanadi, Godavari, Krishna, and Kaveri.
• Includes important hill ranges such as the Javadi, Palconda, Nallamala, and Mahendragiri Hills.

Other Notable Hills and Plateaus

• Nilgiri Hills: Located at the junction of the Western and Eastern Ghats, known for their unique biodiversity and hill stations like Ooty.
• Cardamom Hills and Anaimalai Hills: Part of the Western Ghats in Kerala and Tamil Nadu, rich in flora and fauna.
• Central Highlands: Located east of the Marwar Upland, including the Chambal River basin, bounded by the Aravali range to the west.
• Various smaller plateaus such as the Malwa, Hazaribagh, Ranchi, and Coimbatore plateaus interspersed with hill ranges and river basins. 

Geological and Ecological Significance

• The Peninsular Hills are mostly residual hills, remnants of ancient mountain ranges that have undergone extensive erosion over millions of years.
• The geology is complex, involving Archean, Gondwana, Cuddappah, and Dharwar rock formations.
• These hills influence the climate by intercepting monsoon winds, creating rain shadow areas and affecting river patterns.
• They are home to many endemic and endangered species, making them ecologically vital.
• The Western Ghats, in particular, are recognized as a UNESCO World Heritage Site for their biodiversity.

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