By Jack Clarke
Fellow Lions, I did not need to think hard about my topic. Marshalls, my employer, are a supplier of natural stone and hence I see rocks everywhere. I researched the history of the rocks we will walk on and hope you find the below of some interest.
The geology of the Iberian Peninsula consists of the rock formations on the Iberian Peninsula, which includes Spain, Portugal, Andorra, and Gibraltar. To the west, the peninsula is delimited by the continental boundary formed by the opening of the Atlantic Ocean. A collision of tectonic plates led to the formation of a new mantle. Iberia, which occupied the center of Pangea, the only terrestrial continent at the time, received a new suit made from 310 geologic and 290 million years due to the movement of tectonic plates. It modified the external and internal geology of the peninsula, when the movements gave rise to the destruction of the mantle that existed until that time, between 30 kilometers and 150 kilometers deep, and the formation of a new one today.
The Pyrenees form part of the huge alpine geological system. This 430 kilometre long, roughly east-west striking, intracontinental mountain chain divides France, Spain and Andorra. It has an extended, multi-cycle geological evolution dating back to the Pre Cambrian. The chain's present configuration is due to the collision between the microcontinent Iberia and the southwestern promontory of the European Plate (i.e. Southern France). The two continents were approaching each other since the onset of the Upper Cretaceous about 100 million years ago, and were consequently colliding 55 to 25 million years ago. After its uplift, the chain experienced intense erosion. A cross-section through the chain shows an asymmetric flower-like structure with steeper dips on the French side and more rolling formations on the Spanish side.
The Pyrenees stretch in a westnorthwest-eastsoutheast-direction over 430 km from the Bay of Biscay in the west to the Golf de Lyon and the Golf de Roses in the east, their width across strike varying between 65 and 150 km. They are bounded in the north by the North Pyrenees front, a major thrust fault along which units from the North Pyrenees have been transported over the southernmost part of the Aquitaine Basin their most northern reach. Their southern limit is the South Pyrenees fault. Here, thrust slices from the Sierras Marginales and their lateral equivalents are displaced southward. Yet in a larger, geologically more meaningful sense the Pyrenees continue farther west into the Basque and the Basque-Cantabrian chain. They finally disappear along the continental margin of Asturias. Likewise in the east, they do not just vanish in the Mediterranean, but rather pursue their course via the nappe units of the Corbières into low Languedoc and even into southern Provence. At their far eastern end in Provence, typical pyrenean fold trends are superimposed by alpine structures to be finally cut off by the arc of the western Alps.
The pyrenean chain in the larger sense is nearly a 1,000 km long.