How do we know that coal was not formed in seas?

Answer 1

Coal formation primarily occurs in swampy, low-oxygen environments where plant material accumulates and is buried over millions of years, a process known as coalification. Geological evidence shows that coal deposits are often found in areas that were once lush, terrestrial ecosystems, rather than marine environments. Additionally, the presence of distinct plant fossils, such as ferns and trees, in coal seams further supports its terrestrial origin, as these plants are not typically found in sea environments.