The correct option is 1 and 3 only.
Explanation
Fossil fuels are carbon-rich energy sources formed from the remains of ancient organisms. The specific type of fuel formed depends on the nature of the organic matter, the environment of deposition, and the geological conditions (pressure and temperature) over millions of years.
Statement-wise Analysis:
- Statement 1 is Correct: Coal was formed primarily from the remains of trees, ferns, and other terrestrial vegetation that grew in ancient swamps and peat bogs. Over time, layers of sediment covered this vegetation, and heat and pressure converted it into coal.
- Statement 2 is Incorrect: Petroleum (crude oil) and natural gas were formed primarily from the remains of tiny marine organisms, such as plankton and algae, that settled on the ocean floor. They were not formed exclusively from terrestrial trees. As these organisms were buried under layers of silt and sand, high heat and pressure transformed them into oil and gas.
- Statement 3 is Correct: Once formed, petroleum and natural gas are less dense than water. They tend to migrate upward through porous rock layers (such as sandstone or limestone). This migration continues until the fluids are trapped by an impermeable layer of rock (cap rock), creating a reservoir.
Key Takeaway:
The primary distinction in fossil fuel origin is that coal is derived from terrestrial plant matter, whereas petroleum and natural gas are derived largely from marine microorganisms.