The Carboniferous Period, about 359 to 299 million years ago, was a time of vast tropical wetlands long before dinosaurs appeared. In these coal forests, giant lycopsid trees, horsetails, seed ferns, and tree ferns grew in warm, humid lowlands near the equator. Their remains built up in waterlogged swamps where decay was slow, creating thick layers of peat.
Over millions of years, that buried peat became many of the coal deposits humans later mined for fuel.
Key Facts
- Carboniferous Period: about 359 million to 299 million years ago.
- Coal formation sequence: plant matter → peat → lignite → bituminous coal → anthracite.
- Peat forms when plant material accumulates faster than it fully decomposes.
- High oxygen levels in the late Carboniferous may have reached about 30 percent, compared with about 21 percent today.
- Pressure increases with burial depth, helping squeeze water and gases out of peat during coalification.
- The Carboniferous ended tens of millions of years before the first dinosaurs evolved.
Vocabulary
- Carboniferous Period
- A geologic period from about 359 to 299 million years ago known for extensive swamp forests and major coal formation.
- Peat
- Partly decayed plant material that builds up in wet, oxygen-poor environments and can later become coal.
- Coalification
- The long process in which buried peat is changed by heat, pressure, and time into coal.
- Lycopsid
- An ancient group of vascular plants that included giant tree-like forms common in Carboniferous swamp forests.
- Fossil
- Preserved evidence of past life, such as a body part, leaf impression, track, or trace left in rock.
Common Mistakes to Avoid
- Calling Carboniferous coal forests dinosaur habitats is wrong because the Carboniferous ended long before dinosaurs evolved.
- Assuming coal forms from dead animals is wrong because most coal comes from ancient plant material, especially swamp plants.
- Thinking peat becomes coal quickly is wrong because coalification usually requires deep burial and millions of years.
- Treating all coal as the same material is wrong because coal rank changes with heat, pressure, carbon content, and burial history.
Practice Questions
- 1 The Carboniferous Period lasted from about 359 million to 299 million years ago. How many million years did it last?
- 2 A swamp accumulates peat at an average rate of 1 millimeter per year. If no peat is lost, how many meters of peat could accumulate in 5,000 years?
- 3 Explain why a waterlogged swamp is better than a dry forest floor for preserving plant material that may later become coal.