Introduction

The Heart of Wales Geopark is being created to help you understand one of the most important areas of geology in not only Britain, but the World. It has played a critical part in the historical development of geology and palaeontology, with more than 300 years of study, but unusually for classic areas, major new discoveries continue to this day. It has long been a training ground for undergraduate students, and a magnet for fossil collectors. The research that has been done here is taught in universities around the world, and the most recent discovery of the fossil deposit known as the Castle Bank Biota raises its importance to a truly global scale.

The geopark is centred on an area known as the Builth–Llandrindod Inlier. An inlier is simply an area of older rocks surrounded by younger, and in this case the rocks are from the Ordovician Period, some 455–465 million years old. The rugged landscape of the area, with crags and lumpy hills, reflects the underlying geology... which preserves the complete history of an ancient volcanic island, complete with hundreds of species that lived around it.

During the Ordovician, Wales and England were part of a microcontinent known as Avalonia, drifting north through southern oceans. The ancient Iapetus Ocean to the north gradually sank beneath this island continent, with most of Wales sagging to well below sea level, creating the Welsh Basin. The sediments that filled this basin became the rocks that are now exposed across most of Wales, and the seascape was occasionally interrupted by isolated volcanic islands. Imagine Indonesia, albeit at a time before there was life on land!

Much more has happened since, from continental collisions and mass extinctions, to the recent glaciations of our current Ice Age. This geological prehistory has shaped the Wales we know today, from the slates of the north to the softly rounded hills of the Radnor Forest. The chemistry of the rocks and soils, and the drainage and topography, shapes the biodiversity of the area, from lichens to insects, birds and flowers. The volcanoes have shaped human culture, too, whether that is how the land is farmed, or where we have chosen to live over thousands of years. Llandrindod only exists because of the mineral-rich springs that rise from a buried magma chamber that once fed the geopark's volcano.

The Heart of Wales Geopark may be small in scale, and may lack the grandeur or glamour of some of the world's great geoparks, but this allows the story to be told and understood more completely. It covers a truly unique area for learning about the ancient past and how it has shaped our present, and is still in the stage of active research. We want you to join in with this journey of discovery, learn how to read the rocks, and contribute to our understanding of the mysterious lost world of the Hearth of Wales.