Gower Geology

“Beauty is only skin deep," the old saying goes. But in viewing the spectacular Gower scenery: the sweeping bays of golden sand, the mighty cliffs rising from white-crested sea and the swathes of rare and beautiful flowers which decorate the diverse landscape; it must be remembered that these topographical riches result from the geology that lies deep below its surface.

The Great Tor

The various underlying rock foundations of the Gower Peninsula, not only structure the great variety of coastlines, hills, valleys and bays; they are also one of the major decisive factors in what vegetation grows here.

Underlying Coal or Millstone Grit shales, for instance, give rise to impoverished soils, as does Old Red Sandstone. Limestone beds, on the other hand yield richer soils, affording a greater wealth of flora and, in turn, fauna.

Mewslade

Devonian Old Red Sandstone

The geological events that were to give rise to Gower's famed landscapes began before Carboniferous times, more than 350,000,000 years ago. Britain, then lying close to the equator, was experiencing a tropical monsoonal climate and the area that is now Gower was a vast estuary. This was the Devonian Period and the Old Red Sandstone that formed during that era provides Gower with its oldest rock base.

Rhossili Down

The estuarine river here was rich with sediment washed down from immense mountains by the monsoon rains. Coarser material was also washed down from these bordering mountains and this built up into mini islands that broke the river into many channels. These islands can now be seen as the conglomerates that rise at certain points from Gower's Old Red Sandstone hills.  As the Devonian period came to a close, intense earth movements buckled the Old Red Sandstone into curving hills and valleys.

Carboniferous Limestone

With a further change of climate, the landscape became submerged and brought less sediment to the area.  Warmer and clearer water with coral reef masses were created and limestone began to form from the shells and skeletons from the populated marine life. Particles of lime became more concentrated with the lack of other detritus and sediment.

Caswell

This layer of limestone rock, which grew 800 metres thick in places, was forcefully shaped around the contours of the Old Red Sandstone backbone beneath it, which created structural weaknesses in the Limestone strata. The more the Limestone strata was moulded, the weaker and more prone to erosion it became. Thus, the Carboniferous Limestone that covered the steepest and highest Old Red Sandstone hills soon eroded to reveal the older rock structure beneath it, explaining why all of Gower's higher ground (Rhossili Downs, Cefn Bryn, Ryer's Down and Harding Down) are created from the more ancient Devonian Old Red Sandstone.

Rock diversity

One interesting feature of Gower is that instead of following it, Gower's coastline cuts across this folded bed of Carboniferous Limestone and the traced landscape of Old Red Sandstone beneath it. This reveals various sections and intersections of the rock strata and it is this that gives rise to the great variety of rock formation present on the peninsula.

Where the exposed limestone strata lies vertical on the surface, the cliff appears flat and featureless. Such formations can easily be identified at Thurba Head and the Knave, near Rhossili. Here the cliffs present the blank, sheer rock faces preferred by nesting sea birds. Similarly smooth cliff faces are evidenced when the Limestone strata lie exposed at an angle of 45 degrees towards the sea, for example in the coastline east of Pennard.

Brandy Cove

However, when the strata are inclined inland to such a degree, it is the edges of the strata that are exposed, not its surface, and here cliffs present themselves as a series of sloping ledges. As these ledges can both gather soil and hold rain water, vegetation is readily established, resulting in the quite colourful stretches of coastline such as those near Port-Eynon.

Namurian Millstone Grit and Coal Measures

During the following Namurian period, the sea retreated and the earth's crust bent further. This created heavy erosion that filled the rivers that now flowed over Gower with new detritus (Millstone Grit). Upon this grew an immense forested swampland of mosses, horsetails and ferns.

With upfolding rock pressures, these forests subsided into the rivers. Soil formed upon this new river bed and, in time, further forests grew. This cycle continued time after time to form one of the richest coal seams in the UK.

With the sea level now rising again, much erosion now set in. This erosion created what is now the Burry Estuary and Swansea Bay whilst the harder Upper Measure of this coal seam, Pennant Sandstone, resisted erosion and now form the range of high ground spanning Townhill in Swansea to Penclawdd. This harder Pennant Sandstone was deposited by rivers flowing northwards from huge mountains over south-west England.  Originally blue-grey in colour, the iron content of these rocks soon turned them a rust colour when exposed to the climate.

At the end of this period, some 280 million years ago, much of Gower's shape as we know it today had been formed.

Later geological strata have virtually been eroded completely save for the small outcrop of Triassic rock near Port-Eynon and the greatest geological changes to the area after this date have arisen from sea level changes between the various Ice Ages.

Gower Geology

Ipswichian Raised Beaches

Varying historical sea levels left several raised beaches along Gower's southern coastline, perhaps best evidenced at Foxhole, near Southgate and Brandy Cove. Known as a Patella Beach, these raised Ipswichian-dated beaches can be seen in the fault gully of the rock here as a concrete-like mixture of shell and pebble over a more gravel like substance. The beach takes its name from the fact that Limpets (Patella) are the more common shell found amongst this deposit.

Future change

The erosion of Gower's landscape continues to this day and whilst savage climatic change is held responsible for the shaping and reshaping the peninsula in the past, it is predicted that further rising sea levels and climate change will continue to threaten life on the peninsula and the rest of the world.

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