Are you on Santa’s Naughty or Nice list this year? If all you’ve discovered in the toe of your stocking this morning is a lump of coal, it might not be as terrible a present as you think. Look closely, and you might find that Father Christmas has brought you a fossil plant or two!
Coal is formed from dead and only partially decayed plant material. Essentially it is peat that has been subjected to heat and high pressure changing it from the soft brown material widely used in gardening into the hard black coal.
Reading University Herbarium holds both specimens and photographs of fossil plants:
Lepidodendron fossil in coal
Teaching slide of Lepidodendron
These two are examples of Lepidodendron, a plant fossil commonly found in carboniferous rocks. Known as the ‘scale tree’, the diamond shapes are in fact scars left by the shedding of leaves as the plant grew.
Annularia in coal
One of the old teaching slides for fossil plants
A horse tail
This specimen and photograph are examples of Annularia, which are the leaves of Calamites. Abundant in coal deposits, its closest living relative is Equisetum or Horsetail. (You may already be familiar with Equisetum arvense, which can be particularly invasive.)
A history of the world
But what did the plants of the carboniferous era actually look like? There are plenty of artistic interpretations, like the one below which is part of Ridpath’s “History of the World”, published in New York in 1897. The complete book is available to view online – this image is on page 86.
The diorama above is at the Ruhr Museum in Germany, part of the Zollverein Coal Mine Industrial Complex, which is now a UNESCO World Heritage Site. This is probably one of the best places in Europe to learn about coal all the way from its prehistoric origins right through to its modern industrial history.
Coal in society
Coal has been recognised and an important combustable material for milennia and is mentioned by Theophrastus in his treatise On Stones (Περὶ λίθων) written in the 4th century BC. It has been a key part of global industrialisation but the impact on climate through the release of CO2 and the gradual depletion of global coal reserves means it’s use is now being phased out.
So, if you get coal in your Christmas stocking, rather than a satsuma, think about the 250-350 million years of history your are holding and promise to be better behaved next year.