Explanation: Coal is a fossil fuel formed from the remains of plants that lived millions of years ago. The classification of coal is based on the geological period in which it was formed, which affects its properties and characteristics. In India, coal deposits are classified into three main types based on their age: Carboniferous, Gondwana, and Tertiary.
1. **Carboniferous Coal**: This type of coal is formed during the Carboniferous period, which occurred approximately 300 to 360 million years ago. Carboniferous coal is known for its high quality and is primarily found in the northeastern parts of the world, but not in India.
2. **Gondwana Coal**: Gondwana coal is formed during the Carboniferous and Permian periods, which are older than the Tertiary period. It is the most common type of coal found in India, particularly in the central regions such as Jharkhand, Chhattisgarh, and Madhya Pradesh. Gondwana coal is characterized by its high carbon content and is used extensively in the Indian coal industry.
3. **Tertiary Coal**: Tertiary coal is formed during the Tertiary period, which is relatively younger compared to the Carboniferous and Gondwana periods. The Tertiary period spans from about 66 to 2.6 million years ago. In India, Tertiary coal is primarily found in the northeastern states, including Meghalaya, Assam, Arunachal Pradesh, and Nagaland. This coal is younger and has different characteristics compared to Gondwana coal, often being of lower quality but still valuable for certain industrial applications.
The northeastern states of India, particularly Meghalaya, are known for their Tertiary coal deposits. The coal found in these regions is often lignite or sub-bituminous, which are younger and less metamorphosed forms of coal. These deposits are significant for the local economy and contribute to the energy needs of the region.
Understanding the geological periods and the types of coal associated with them is crucial for comprehending the distribution and characteristics of coal deposits in India. This knowledge is essential for students preparing for competitive examinations such as the UPSC Civil Services, GATE Mining Engineering, and State PSC Exams, where questions on Indian geography and natural resources are common.