The 7.3 km long circular route takes you back to a time when Cornwall was covered by sea and then became a Europe-wide mountain range. The sedimentary rocks of this area around Portreath were deposited in a deep marine environment during the Devonian age (ca. 393 - 373 million years):
Greywacken: Gray rock with fine to coarse grains (0.3 - 2 mm; 0.01 - 0.08 inch), consisting of quartz, feldspars and fragments of foreign rocks. In some cases, shiny/shimmering components can be seen (mica), the rocks form layers and banks.
Siltstones: Light gray rock with fine grains (<0.063 mm; <0.002 inch) that are not visible to the naked eye. Layers can be recognized based on the color difference.
Slate: Gray to black, sometimes slightly red to greenish colored rocks with very fine grains (<0.02 mm, <0.001 inch), the rocks appear foliated with very thin layers, often alternating with greywackes.
The originally horizontal sedimentary layers of Cornwall were tectonically overprinted around 323 - 299 million years ago during the Variscan orogeny (mountain formation). During this time, the southern major continent Gondwana collided with the northern major continents Laurentia and Baltica as well as smaller continent fragments (terranes) such as Avalonia and Amorica. The orogeny ended approximately 270 million years ago with the formation of the supercontinent Pangea. Due to the pressure from the south, the sedimentary rocks were compressed, folded and internally transformed under increasing temperatures. This is how slates emerged from the original claystones. There are no deposits in the area for the period between the formation of the Devonian rocks until 3 million years ago. During the Ice Age 3 million years ago, the region of modern-day Cornwall lay in a tundra area south of the glaciers that covered the Northern Hemisphere. Periglacial deposits from this period can be observed on the cliffs.
Translated by Google •
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