Coal Swamps and Volcanoes
With time, the freshwater lakes which characterised the Devonian period disappeared and the age of the coal swamp began - the Carboniferous. At this time, Scotland was located on the equator, so the widespread tropical vegetation which clothed the landscape flourished in response to the hot and humid conditions. The early part of this geological period was marked by vast outpourings of lava that spewed out across the Midland Valley to build, for example, the Campsie Fells and Gargunnock Hills.
The step-like profile of these hills reflects their structure, built as they are of layer upon layer of lava. Around volcanoes in the Midland Valley, tropical swamps developed made up of many species of trees and ferns, most of which are long extinct. As the individual trees of these ancient tropical forests died, they fell into the swamp, eventually to form layers rich in organic carbon. As more sediment accumulated on top, these carbon-rich layers were compressed to form coal. Vast riches of fossil fuel accumulated during this period, which were, some 350 million years later, to bankroll the Industrial Revolution in Scotland. Exploitation of these resources continues today and geologists have built up a detailed knowledge of the nature and distribution of these deposits.
The first action to conserve Scotland's geological heritage was initiated in 1887 when a number of fossil tree stumps were unearthed in what is now Victoria Park in Glasgow. In recognition of the great scientific and cultural significance of these tree stumps, a building was erected to protect them from fossil collectors and the ravages of the elements. This building was recently renovated by Glasgow City Council.
Another jewel from the Carboniferous period was found in Bathgate, near Edinburgh. It was here that a rare fossil called 'Lizzie' or Westlothiana lizziae was found. Lizzie is the fossilised remains of the oldest reptile to be found anywhere in the world and its discovery has been described as one of the finds of the century. It was previously thought that reptiles evolved later in the Carboniferous period, so this chance find has overturned evolutionary theory of the early development of this important animal group.