Most of the rocks making up Pembrokeshire are over 225 Million years old from the Palaeozoic era. To the north lie Cambrian sandstones used to build St David's cathedral, hard Ordovician shales and mudstones, and Pre-Cambrian volcanic rocks which form rocky outcrops. To the south are Silurian volcanics, such as form Skomer Island, red Devonian sandstones and Carboniferous limestone and coal measures. The North-South divide is recognised in a line called 'Landsker's Line' which runs from approximately Newgale to Treffgarne. To the south is the 'softer' landscape with rolling hills and lush fields. This is often called 'Little England'. It was colonised by the Normans, most towns lie within it and have English names - it is English-speaking. To the north the land is more rugged, soils poor and acidic, and the influence is Celtic and Welsh-speaking. Below is a geological map of Pembrokeshire which shows the division of rocks types. The hard Ordovician rocks are shown in purple with Ordovician volcanics in red, Pre-Cambrian in pink, Cambrian in blue.
Pembrokeshire is exceptional geologically not only for the diversity of rock types, but because erosion by the sea has allowed these rocks to be exposed in spectacular cliffs and bays. Following the Pembrokeshire Coast Path every headland reveals new wonders and sights, which is enhanced by a knowledge of geology.
The North-South divide is also evident in the forces acting on the rocks. The north has been influenced by the Caledonian orogeny (orogeny = mountain building event) in which the Caledonides, a huge mountain belt, formed when the Iapetus Ocean closed and the North American continent collided with Avalonia and Baltica. The south has been more influenced by the later Variscan orogeny which occurred when the Rheic Ocean closed.
Recent Ice ages have left their mark on Pembrokeshire. Glacial till, deposits from melting ice sheets and glaciers, lie on top of older rock strata. At the end of the last Ice Age (approximately 10,000 years ago) melting ice sheets to the north that covered parts of Wales and the Irish Sea cut deep valleys and estuaries, such as the Gwaun and Cleddau rivers which are dwarfed by the size of their valleys - called 'misfit' rivers.
The North-South divide is also evident in the forces acting on the rocks. The north has been influenced by the Caledonian orogeny (orogeny = mountain building event) in which the Caledonides, a huge mountain belt, formed when the Iapetus Ocean closed and the North American continent collided with Avalonia and Baltica. The south has been more influenced by the later Variscan orogeny which occurred when the Rheic Ocean closed.
Recent Ice ages have left their mark on Pembrokeshire. Glacial till, deposits from melting ice sheets and glaciers, lie on top of older rock strata. At the end of the last Ice Age (approximately 10,000 years ago) melting ice sheets to the north that covered parts of Wales and the Irish Sea cut deep valleys and estuaries, such as the Gwaun and Cleddau rivers which are dwarfed by the size of their valleys - called 'misfit' rivers.
Disclaimer: This artists' collective has been created for educational purposes only. While the members are real artists, they have been brought together as a fictitious group to highlight their relationship with Pembrokeshire.