The geology of Gower gives rise to its variety of landscapes. To understand how the Gower landscape has been shaped by its geology we need to look back in time to over 300 million years ago. When you think that the earliest humans only began to appear on the Earth around 5 million years ago, then it soon becomes clear that the story of Gower’s landscape is a very ancient one indeed!
Most of Gower is made up of Old Red Sandstone and Limestone. These rocks formed at a time when Britain lay closer to the equator and so experienced a more tropical climate, around 300-350 million years ago (known as the Carboniferous period). The Old Red Sandstone formed earliest with the Limestone forming on top. Earth movements and erosion over millions of years have shaped these rocks to create the landscape we see today.
Around 250 million years ago an immense event occurred which created the Gower Peninsula. This event is known as the Variscan Orogeny. At this time much of the land on Earth existed as two continents. During the Variscan Orogeny the two continents collided to form one supercontinent called Pangea. This would have been a slow process, but nonetheless had an enormous impact, forming the Variscan mountain belt. Along with the Gower Peninsula, this mountain belt also includes the uplands of Portugal and western Spain, southwest Ireland, Cornwall, Devon, Pembrokeshire and the Vale of Glamorgan.
Gower, as we know it today, is the result of millions of years of earth movements and erosion. The Old Red Sandstone, the oldest rock, has been shaped to create curving hills and valleys. The Limestone, which formed on top, has been eroded in places to reveal the older sandstone, such as at Rhossili and Cefn Bryn. Weaknesses in the Limestone have also made it more prone to erosion in places, leading to the formation of caves and underground rivers such as those at Bishopston Valley.
In some places the younger and softer rocks have been eroded by the sea to form bays, such as those at Port Eynon, Oxwich and Swansea.
The highest and youngest Carboniferous rocks appear in north and eastern Gower – for example, around Penclawdd and in the Clyne Valley, where coal and ironstones have been mined.
A glacier is a huge mass of ice that slowly moves downhill. Glaciers are found at the north and south poles and around the world at high altitudes, even on the tops of mountains in very warm countries. Glaciation includes the processes that cause glaciers to form and those that help to shape the landscape. The formation, movement and melting of glaciers has been causing the landscape around us to change for millions of years. The last glacial period, known as the last Ice Age, brought about significant changes to the British landscape. This occurred from approximately 110,000 to 12,000 years ago during the period known as the Pleistocene.
In Wales, the Ice Age reached its peak about 20,000 years ago when much of Wales was submerged beneath large ice sheets. The glaciers had mostly melted by about 11,500 years ago.
The Ice Age did not impact as heavily on Gower as it did elsewhere in Britain. Not only did South Gower escape the ice, but the hard ancient rocks were not changed much by the glacial processes. The glaciers did however deposit sediment as they moved and water channels were formed as the ice melted.
For example, Killay Marsh is most likely a glacial meltwater channel. This means that when the glaciers melted the vast amounts of water eroded the ground and cut out a deep, steep-sided valley. Today, it contains superb examples of many threatened and protected wetland habitats. At the foot of the Cefn Bryn ridge is Broad Pool, also formed during the Ice Age. It is quite a shallow pool of water and is now a nature reserve, notable for the great variety of species that it attracts.
The Gower Peninsula has been occupied since before the end of the last Ice Age. As a result there are many ancient sites and historical features in the landscape. This includes Arthur’s Stone, on the top of Cefn Bryn. This is most likely a glacial erratic, meaning that glacial ice carried this large rock some distance before depositing it on top of Cefn Bryn. The Neolithic people then excavated underneath the rock and placed upright stones as supports to create a burial chamber.
Importance of Gower’s geology
The geology of Gower is nationally significant, with 13 protected Sites of Special Scientific Interest (SSSIs) designated for geological or geomorphological reasons, often in conjunction with biological reasons Geology was also a significant factor in the decision to designate Gower an Area of Outstanding Natural Beauty (AONB) in 1956, one of the first of such areas to be established.
The geology of Gower has given rise to the wide variety of beautiful landscapes – from the dramatic limestone scenery of the south between Worms Head and Oxwich Bay, to the extensive mudflats, salt marshes and dune systems in the north. Inland, the most prominent features are the large areas of common dominated by sandstone heath ridges, including the Old Red Sandstone ridge of Cefn Bryn which rises to 178 metres above sea level.