had taken place, were called the Pyrenees." Geography Political divisions The Spanish Pyrenees are part of the following provinces, from east to west: Girona, Barcelona, Lleida (all in Catalonia), Huesca (in Aragon), Navarra (in Navarre). The French Pyrenees are part of the following départements, from east to west: Pyrénées-Orientales (also known as Northern Catalonia), Aude, Ariège, Haute-Garonne, Hautes-Pyrénées, and Pyrénées-Atlantiques (the latter two of which include the Pyrenees National Park). The independent principality of Andorra is sandwiched in the eastern portion of the mountain range between the Spanish Pyrenees and French Pyrenees. Physiographical divisions Physiographically, the Pyrenees may be divided into three sections: the Atlantic (or Western), the Central, and the Eastern Pyrenees. Together, they form a distinct physiographic province of the larger Alpine System division. In the Western Pyrenees, from the Basque mountains near the Bay of Biscay of the Atlantic Ocean, the average elevation gradually increases from west to east. The Central Pyrenees extend eastward from the Somport pass to the Aran Valley, and they include the highest summits of this range: Pico de Aneto in the Maladeta ridge, Pico Posets , Monte Perdido . In the Eastern Pyrenees, with the exception of one break at the eastern extremity of the Pyrénées Ariégeoises in the Ariège area, the mean elevation is remarkably uniform until a sudden decline occurs in the easternmost portion of the chain known as the Albères. Foothills Most foothills of the Pyrenees are on the Spanish side, where there is a large and complex system of ranges stretching from Spanish Navarre, across northern Aragon and into Catalonia, almost reaching the Mediterranean coast with summits reaching . At the eastern end on the southern side lies a distinct area known as the Sub-Pyrenees. On the French side the slopes of the main range descend abruptly and there are no foothills except in the Corbières Massif in the northeastern corner of the mountain system. Geology The Pyrenees are older than the Alps: their sediments were first deposited in coastal basins during the Paleozoic and Mesozoic eras. Between 100 and 150 million years ago, during the Lower Cretaceous Period, the Bay of Biscay fanned out, pushing present-day Spain against France and applying intense compressional pressure to large layers of sedimentary rock. The intense pressure and uplifting of the Earth's crust first affected the eastern part and moved progressively to the entire chain, culminating in the Eocene Epoch. The