Stonehenge: Geology and prehistory

Geological interest in Stonehenge includes not only the main structural components of the monument but also large amounts of stone either used to assist construction; or present as waste from stone-working, or as artefacts left at the site. One suite of rocks, including Chilmark Ragstone, Upper Greensand sandstone and two types of sarsen, can be assembled from localities in Wiltshire, but not without transporting sarsen blocks weighing up to 50 tonnes over a distance of some 40 km. In contrast, the 'bluestones', including dolerites, rhyolites, volcanic ashes and sandstones, originated in southwest Wales, with the bulk of the material coming from a small area in the eastern Preseli Hills, a distance of approximately 400 km from Stonehenge. The lack of evidence for Quaternary glaciation in south Wiltshire means that glacial transport cannot explain the occurrence of this Welsh material on Salisbury Plain. It must therefore have been brought there by the builders of Stonehenge. A brief review of the technical achievements and artistic traditions of the later Neolithic period and the early Bronze Age, reveals the building of Stonehenge as an undertaking consistent with the rich cultural context of these times.