THE IBERIAN PENINSULA Iberian Peninsula, which includes the two countries of Spain and Portugal, has an area of 226,000 square miles. Its central part, which belongs to the zone of ancient massifs and is known as the Meseta, consists of a plateau with a height of over 2,000 feet. On the north-east, the Meseta is bordered by the Iberian mountains which separate it from the basin of the Ebro ; and on the south-east by the Sierra Morena which overlooks the basin of the Guadalquivir, and is in reality only the escarpment of the plateau. The surface of the Meseta consists of great plains separated from one another by mountain ranges which have a general trend from south-west to north-east. Of these ranges the most important are the Sierra de Gredos and the Sierra de Guadarrama, which separate the plains of Old Castile from those of New Castile. In the north-west, in Galicia and in Upper Portugal, the rocks of which the mountains consist are of Archaean age ; in the south-west they belong in the main to early Palaeozoic times; and in the north-east and east they were formed during the Secondary period. The plains of Old and New Castile are overlain by Tertiary deposits, as are the basins of the Guadalquivir and the Ebro, the latter of which is cut off from the sea by the mountains of Catalonia. To the south of these moun tains, the plateau withdraws from the seaboard sufficiently far to allow the formation of the narrow coastal plain of Valencia. On the west it slopes down to the plain of Lower Portugal. The basin of the Ebro is bounded on the north by the Cantabrian mountains and the Pyrenees, while to the south of the Guadal quivir is the Sierra Nevada. These ranges were folded during the
Tertiary period, and consist in the main of old rocks, flanked in places by later formations.
CLIMATE.—Although the Iberian Peninsula is almost entirely surrounded by water, the direct influence of the ocean upon its climate is comparatively slight, and is felt mainly upon the north and north-west coasts where the range of temperature between summer and winter is less than in any other part of the peninsula. There, the January mean (at sea-level) varies from 46°F. to 50°F., while that of July lies between 68°F. and 70°F. On the plateau the rangelis much greater, the summers being hotter and the winters colder. At Madrid, for example, the mean temperature for January is 40°F. and for July 76°F. In Andalusia and along the Mediter ranean seaboard the summers are everywhere hot, the July mean in the lowlands ranging from 75°F. to 80°F. To the south of the Meseta, however, the winters are somewhat warmer than they are along the north-east coast, the January mean in the former region being above, and in the latter below, 50°F. Except on the north and north-west coasts, which have from 30 to 60 inches, the annual precipitation is slight, and only occurs during the winter half of the year. In the south-west the amount received does not exceed 30 inches, while on the plateau and along the Mediterranean coast it is generally less than 20 inches.