359 – 299 million years ago
During the Carboniferous, Scotland lay near the equator in a position akin to central Africa, and therefore had a hot climate. The northern parts of Scotland were upland areas and the southern parts of Scotland were lower lying. Further to the north and west lay the North American continent, to which Scotland was joined, and to the south of what we know as England, lay a large ocean.
During the Carboniferous, the sea level rose and fell several times. Therefore there were times when southern Scotland lay underwater, covered by a shallow, warm sea. At other times this area lay above sea level.
Scotland hasn’t always been on the same postion on the face of the Earth and has not always had the same outline. This map shows how ‘Scotland’ may have looked during the Carboniferous. Scotland’s present outline has been drawn on the map to help you visualise where the Carboniferous rocks that we find today were formed in relation to the surrounding continent and seas.
When below sea level, the area was covered in sand and mud that was washed into the sea, leading to the formation of rocks such as sandstone, mudstone, and shale. Limestone also formed in part through the accumulation of dead sea creatures, but also through the precipitation of calcium carbonate in the tropical conditions. The shallow tropical seas of Carboniferous Scotland, much akin to the present day Bahamas, were full of life and much of this life became preserved as fossils in the rocks, including shellfish, corals, crinoids, sharks and other fish. When above sea level, the land was covered by tropical swamps, where forests of large trees, that were very unlike modern trees, flourished. Giant-sized centipedes, dragonflies and spiders ruled the landscape along with amphibian and early reptiles, the forerunners of the dinosaurs. Over time, the remains of trees that had fallen into the swamps were buried deeply and compacted, eventually forming peat, and finally coal.
Volcanic activity was another important feature of the Carboniferous. The continent at this time was being ‘stretched’, allowing magma to well up from the mantle to form many volcanoes. The remains of these volcanoes dot the landscape of southern Scotland; the extinct Arthur’s Seat volcano in Edinburgh is a good example.