The Fairy-Land of Science · Lecture VIII, part 2 · Part 8: Lecture VIII: The history of a piece of coal
23. Giant forests of long ago, and a swamp that makes peat
Goal: Your child can describe the giant plants of the coal forests and explain how dead plants in a swamp pile up into peat that can become coal.
You'll need
- Pictures of club-moss and horsetail (a free online search; or find them on a walk)
- A clear jar, a handful of dead leaves, some soil and some sand
- A stack of heavy books
- Science notebook and pencils
What's in the book
Pages 179 to 185, with a full-page picture of a coal forest. The coal trees were giant relatives of today's tiny club-mosses and horsetails (scaly Lepidodendron, seal-marked Sigillaria, and Calamites); the forests were quiet, with no flowers or birds; and the Great Dismal Swamp in Virginia shows how dead plants pile up as peat, kept clean of mud, ready to become coal.
The lesson, step by step
Hook question
SayImagine a forest of trees as tall as a house, but they are really giant mosses and horsetails. What would it sound like?
Look at the picture of a coal forest (Fig. 51) facing page 180.
Read together
Read page 179.
the huge trees of the coal-forests, of which we sometimes find trunks in the coal-mines from ten to fifty feet long, are only represented on the earth now by small insignificant plants, scarcely ever more than two feet, and often not many inches high.
Look at the little club-moss in Fig. 50. Then read page 180:
It has been called Sigillaria, because it has marks like seals (sigillum, a seal) all up the trunk
The quiet forest
Read or tell pages 182 and 183. Buckley says there were no people, lions or birds; only a few frog-like animals croaking and a cricket chirping. Horsetails that are now a foot high grew 20 feet tall.
If you can, find real horsetails (they grow in damp ditches) or a club-moss on a walk and draw one.
The Great Dismal Swamp
Read pages 183 and 184.
The whole place is so still, gloomy, and desolate, that it goes by the name of the "Great Dismal Swamp,"
Find Virginia and North Carolina on a map. In the swamp, dead leaves and stems pile up year after year as soft black peat. The thick reeds round the edge strain out the mud, so the peat stays pure plant.
we know that peat when dried becomes firm and makes an excellent fire
Try it: layers that get squashed
In the jar, put a layer of soil (the old ground), then a thick layer of dead leaves (the swamp plants), then sand (the sea that later covered it). Press down hard on top with your hand. See how much thinner the leaf layer gets? Over millions of years, the weight of rock above squashed the peat into hard coal. Pile the books on top of a few leaves between paper and check them in a week.
Tell it back and check
Your child tells back how a swamp can turn into coal. Then ask:
1. Which little plants of today are relatives of the coal trees?
2. What is peat?
3. Why was the peat in the swamp not muddy?
What we know now
The coal forests grew about 300 million years ago, long before the dinosaurs. Buckley thinks the giant club-mosses were crowded out by flowering plants, but most of them had disappeared long before flowering plants appeared. The Great Dismal Swamp is still there, now a wildlife refuge.
Afterwards
Notice it this week: look for moss, ferns and horsetails in damp places, and for dead leaves rotting into dark soil under trees.
Tip
The scientific names are long. Use the picture names instead: "the scaly tree," "the seal tree" and "the giant horsetail."
Answers to the book's problems
1. Club-mosses and horsetails. 2. A thick, soft, black layer of dead plants that have piled up in a swamp. 3. The thick reeds and ferns round the edge strained the mud out of the streams flowing in.
Worked out for this site from the scan. If a number in your copy differs, trust the book.