Tree stumps in sandstone, Glasgow

Around 300 million years ago evidence (from magnetism in rocks) shows that what we now call Britain lay near to the equator. Deposits preserved from that time show that much of the land was low-lying swamp covered by tropical rain forest (see reconstruction photo below).

The peaty remains of of this vegetation has been compressed to form coal seams in many places such as in Yorkshire and South Wales. Coal has been mined for fuel for hundreds of years.

These trees were surrounded by sand and mud, and buried by a river flood; the soft “pith” inside the trunks rotted quickly, so the hollow trunks and roots were filled by more sand, which hardened to produce the fossils we see today.