Correct Option
The correct option isAbout 300 million years ago
Explanation
The process of coal formation, known as carbonisation, involves the slow conversion of dead vegetation into coal under conditions of high pressure and temperature. This geological process requires millions of years to transform organic matter into carbon-rich fossil fuels.
Detailed Analysis
- About 300 million years ago (Correct): This timeframe corresponds to the Carboniferous period. During this era, the Earth was covered with dense forests in low-lying wetland areas. Due to natural processes such as flooding and tectonic shifts, these forests were buried under soil. Over time, as more soil deposited over them, they were compressed. The temperature also rose as they sank deeper. Under high pressure and high temperature, these dead plants were slowly converted into coal.
- About 1000 years ago (Incorrect): This period is geologically insignificant for the formation of fossil fuels like coal, which require millions of years of compression and thermal alteration.
- About 1 million years ago (Incorrect): This corresponds to the Pleistocene epoch. While peat formation occurred, it is insufficient time for the complete geological transformation into high-grade coal deposits.
- About 50 million years ago (Incorrect): While some coal deposits (Tertiary coal) formed during this period, the primary and most extensive coal-forming age associated with the burial of dense forests is the Carboniferous period (approx. 300–360 million years ago).
Key Takeaway: Coal is a fossil fuel formed primarily during the Carboniferous period (approximately 300 million years ago) through the process of carbonisation of buried vegetation.