The varied and beautiful landscape of Pembrokeshire has been sculpted over millions of years from the underlying rocks, giving us the unrivalled views of mountains, valleys and sea cliffs that are an integral part of the county today. The human heritage is also imprinted on the geological landscape.
Cyfrol sy’n astudiaeth o ddaeareg sir Benfro. Mae tirwedd arfordif Penfro wedi cael ei llunio a’i cherflunio dros filiynau o flynyddoedd, gan greu’r mynyddoedd, dyffrynnoedd a chlogwyni sy’n rhan annatod o’r sir.
Having tutored Earth Science students at the Open University for many years, the author appreciates the significance of ‘enigmatic discussion’ of the origin and ‘riddle’ of rocks, and he approaches geology in the field in this spirit of enquiry. This particular guide on the subject relating to Pembrokeshire is intended for students, walkers, amateur geologists and anyone who would like to discover the wonderful geology of this coastline.
He starts with a brief outline of the geological history of south-west Wales, prefaced by an introduction to the shift, over millions of years, in plate tectonics, of magma rising, and the opening and closing of the Iapetus Ocean which shunted, drifted and pulled together what we now recognise as the British Isles.
The chapters are organised chronologically, starting with the oldest Precambrian outcrops and concluding with the deposits and landforms of the Pleistocene Ice Age. Each chapter begins with an overview of the region and then focuses on particular sites of interest and directions on how to visit them. One of many examples to highlight is the chapter on the Precambrian and Cambrian rocks of the St. David’s Peninsula whose cliffs ‘display some magnificent geological sections through some of the oldest rocks in Wales.’
For the complete beginner, some of the more technical geological terms which might baffle and bemuse are thoughtfully highlighted in bold and defined in a thorough glossary: Alkali feldspar, Gash Breccia, Variscan orogeny, Flexural slip, Seat Earth, Liquefaction, Scoriaceous and Bioturbation, to name a few.
The text also benefits from diagrams and colour plates illustrating specific rock formations. There are some lovely images here: the cliffs of Caerbwdy sandstone at Porth Glais, the columnar dolerite sill at Point St. John, the disused slate workings at Abereiddi, the block of ‘spotted dolerite’ and the shattered tors on Carn Menyn, harmonic folding in the cliffs of Pen-yr-Afr, St. Govan’s chapel at the foot of limestone cliffs, Elegug rocks (wonderful sea stacks much loved by sea birds), and the Green Bridge of Wales, a natural arch of carboniferous limestone near Castlemartin.
This is a complex and fascinating subject, and this volume is perhaps more suited to the amateur geologist and student, rather than someone stepping into the subject for the first time. Having said that, by highlighting individual places the reader and walker can visit and explore, the author attempts to open it out to the novice who is starting to read the story of these ancient rocks. Just remember to keep the glossary in your pocket.