How is coal primarily formed?

Coal is primarily formed from the remains of plants, specifically trees and other vegetation that thrived in dense forests, particularly in low-lying wetland areas. Over millions of years, these plant materials accumulate and undergo a process called carbonization, where heat and pressure transform them into peat and then into coal. This process typically occurs in environments where conditions are conducive to preserving plant material, such as swamps, where the accumulation of organic matter outpaces its decay due to the anaerobic (low oxygen) conditions.

In this context, while marine animals contribute to the formation of oil and natural gas through different processes, they do not play a significant role in coal formation. Mineral deposits in mountains do not relate to the biological origins of coal but rather to geological processes unrelated to plant material. The compression of carbon in the Earth's crust is a vague description and does not specifically refer to the biological and geological processes required for coal formation.