Coal forests

The Carboniferous is the only period of geological time named after something we burn. Its name means coal-bearing, and it comes from England, after the rich coal deposits there. It lasted from 358.86 to 298.9 million years ago. Its coal is found across northern Europe, Asia and eastern North America.

For much of the Carboniferous, the ground that is now Britain lay near the equator, with tropical swamps across it. Those swamps left the coal that later powered the industrial revolution.

Why it did not rot

Normally, dead plants rot away. In the Carboniferous swamps, fallen plant material lay under water, and when the sea flooded in it was buried under layers of sediment before it could decay. Over millions of years, pressure and heat turned it to coal. Each seam is a buried forest floor, and the rock between seams was laid down when the sea covered it.

The biggest bug that ever lived

The forests were also home to a giant. In January 2018 a block of sandstone fell from a cliff onto the beach at Howick Bay in Northumberland. Inside was a piece of shed skin, 76 by 36 cm, from Arthropleura, a giant relative of the millipedes. The animal that left it is estimated to have been up to 2.63 metres long and 55 cm wide: the largest arthropod known from the whole of Earth’s history.

Eggs on dry land

The Carboniferous also saw one of the great inventions in the history of life: the amniote egg. It allowed the ancestors of reptiles, birds and mammals to lay eggs on land without them drying out. You can follow that story in Onto the land and Before the dinosaurs.