Page:EB1911 - Volume 22.djvu/149

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PHYSICAL FEATURES]
135
PORTUGAL


(3511 ft.), between the Vouga and the Dao; and the Serra da Lapa (3215 ft.), which gives rise to the Paiva, Tavora, Vouga and Dao. South of these ranges, but nominally included in the same system, is the Serra da Estrella, the loftiest ridge in Portugal (6532 ft.). The Estrella Mountains, which enclose the headwaters of the Mondego in a deep ravine, stretch from north-east-to south-west and are continued in the same direction by the Serra de Lousa (3944 ft.). They form the last link in the chain of mountain ranges, known to Spanish geographers as the Carpetano-Vetonica, which extends across the centre of the Peninsula from east to west. The greater part of the Serra da Estrella constitutes the watershed between the Mondego and Zezere. Lesser ranges, which are included in the Beirene system and vary in height from 2000 to goo ft., are the Mesas, between the rivers C6a and Zezere; the uardunha and Moradal, separating the Zezere from the Ponsul and Ocreza, tributaries of the Tagus; the Serra do Aire, and various ridges which stretch south-westward as far as the mountains of Cintra (q.'v.). The Transtagine Mountains cannot rightly be described as ~a single system, as they consist for the most part of isolated ranges or masszfs. The Serra da Arrabida (1637 ft.) rises between Cape Espichel and Setubal. Sao Mamede (3363 ft.), with the parallel and lower Serra de Portalegre, extends along part of the frontier of northern Alemtejo. Ossa (2129 ft.), Caixeiro (1483 ft.), Monfurado (1378 ft.) and Mendro (1332 ft.) form the high ground between the rivers Sado, Sorraia and Guadiana. East of the Guadiana the outliers of the Spanish Sierra Morena enter Portuguese territory. The Serra Grandola and Monte Cercal, two low ranges stretching from north to south, skirt the coast of southern Estremadura. In the extreme south the ranges are more closely massed together. They include Monchique, with the peak of Foya or Foia (2963 ft.), and various lower ranges. There are numerous large expanses of level country, the most notable of these being the plains (campus) of the Tagus valley, and of Aviz or Benavilla, Beja and Ourique, in Alemtejo; the high plateaux (cimas) of Mogadouro in Traz-os-Montes and Ourem between the Tagus and the upper Sorraia; the highly cultivated lowlands (veigas) of Chaves and Valenga do Minho in the extreme north; and the marshy flats (baixas) along the coast of Alemtejo and the southern shore of the lower Tagus.

The three principal rivers which How through Portugal to the sea-the Douro, Tagus and Guadiana-are described in separate articles. The chief Portuguese tributaries of the Douro are the Tamega, Tua and Sabor on the north, the Agueda, Coa and Paiva on the south; of the Tagus, the Ocreza, Ponsul and Zezere on the north, the Niza and Sorraia on the south, while into the Guadiana, on its right or Portuguese bank, flow the Caia, Degebe, Cobres, Oeiras and Vascao. The whole country drains into the Atlantic, to which all the main rivers flow in a westerly direction except the Guadiana, which turns south by east in the lower art of its course. The Minho (Spanish Mina) is the most northerly river of Portugal, and in size and importance is only inferior to the three great waterways already mentioned. It rises in the highlands of Galicia, and, after forming for some distance the boundary between that province and Entre-Minho-e-Douro, falls into the sea below the port of Caminha, Its length is 170 m. Small coasters can ascend the river as far as Salvatierra in Galicia (20 m.), but larger vessels are excluded by a sandy bar at the mouth. Between the Minho and Douro the chief rivers are the Lima (Spanish Limia or Antela), which also rises in Galicia, and reaches the sea at Vianna do Castello; the Cavado, which receives the Homem on the right, and forms the port of Espozende in its estuary; and the Ave, which rises in the Serra da Cabreira and issues at the port of Villa do Conde. Between the Douro and Tagus the Vouga rises in the Serra da Lapa and reaches the sea through the lagoon of Aveiro; the Mondego flows north-east through a long ravine in the Serra da Estrella, and then bends back so as to flow west-south-west. Its estuary contains the im ortant harbour of Figueira da Foz; its chief tributaries are the Igao on the right, and the Alva, Ceira and Arunca on the left; its length is 125 m. of which 52 m. are navigable by small coasters. Several comparatively unimportant streams, chief among which are the Liz and Sizandro, enter the Atlantic between the mouths of the Mondego and Tagus. Between the Tagus and Cape St: Vincent the principal rivers are the Sado, which IS formed by the junction of several lesser streams and flows north-west to the port of Setubal; and the Mira, which takes a similar direction from its headwaters south of Monte Vigia to the port of Villa Nova de Milfontes. On the south coast the united waters of the Odelouca and Silves form the harbour of Villa Nova de Portimao, and the Algoz, Algibre or Quarteira, and the Asseca flow into the sea farther east. Portugal abounds in hot and medicinal springs, such as those of Caldas de Monchique, Caldas da Rainha and Vidago.

Qeologyf-By far the greater part of Portugal is occupied by ancient rocks of Archean and Palaeozoic age, and by eruptive masses which probably belong to various periods. All the higher mountains are formed of these rocks, and it is only near the coast and in the plain of the Tagus that later deposits are found. The Mesozoic beds form an irregular triangle extending from Lisbon and Torres Novas on the south to Oporto on the north. There are also a narrow strip along the southern shores of the Algarve and a few smaller patches along"the western coast. The Tertiary deposits cover the plain of the Tagus and are found in other low-lying areas near the coast. Of the Lower Palaeozoic rocks the Ordovician appears to be the most widely-spread. Large areas have been referred to the Cambrian, but it is only at Villa Boim, about 6 m. W.S.W. of Elvas, that Cambrian fossils have been found. The Ordovician beds have yielded fossils in several places, Vallongo and Bussaco being amongst the best-known localities. The succession is similar to that of Brittany and Spain. Supposed Silurian beds have been described at Portalegre, and in the same neighbourhood Devonian fossils have been found. The Lower Carboniferous, which belongs to the “ Culm ” facies so widely spread in central Europe, occupies a wide area in southern Portugal; but the Upper Carboniferous is very restricted in extent, and occurs in small basins like those of the Central Plateau of France, resting unconformable upon the rocks below. The deposits in these basins consist largely of coarse sandstones and conglomerates, amongst which lie seams of coal. It is possible that some of these deposits may belong to the Permian or at least to the Perma-Carboniferous. Of the Mesozoic systems the Jurassic is the rnost widely-spread. Supposed Triassic beds are found, but they are confined chiefly to the eastern margin of the Mesozoic area north of Lisbon. The jurassic deposits are partly marine and partly fresh-water or terrestrial, including beds of lignite. On the whole, excepting in eastern Algarve, the Upper jurassic beds indicate the neighbourhood of a shore-line. The Cretaceous system is very limited in extent. Its most interesting feature is the occurrence near its summit, north of Cape Mondego, of sands and gravels containing plant remains. Here both Cretaceous and Tertiary forms are found, and the Mondego beds seem to represent the passage between the two systems. At the close of the Cretaceous period great eruptions of basalt and basaltic tuff took place, especially in the Lisbon area. The volcanic rocks then formed are followed by marine deposits of Oligocene 'and Miocene age. Towards the north these are associated with fresh-water limestones, indicating the presence of land in that direction. Marine Pliocene beds occur at the mouth of the Tagus. The contemporaneous beds inland are of freshwater origin. Eruptive masses of various age are found in many localities. The Cintra granite sends veins into the base of the Upper urassic, and is very probably of Tertiary age. The Serra de onchique is petrographic ally of great interest. It consists chiefly of elaeolite-syenite and other rocks derived from the same igneous magma.

Climate.-The climate of Portugal is equable and temperate. Lisbon, Coimbra, Evora and Oporto have mean temperatures between 60° and 61-5° F., and the daily variation nowhere exceeds 23°. This equability of temperature is partly caused by the very heavy rainfall precipitated on Portugal as one of the westernmost countries of Europe and the one most exposed to the Atlantic. The rainfall has been as heavy as 16 ft. in a year, and sometimes, as in the winter of 1909*1910, great damage is wrought by floods. Heavy fogs are also common along the coast, rendering it dangerous to ships. The rainfall is heaviest in the north and on the Serra da Estrella; it is least in Algarve. A fine climate and equability of temperature are not universal in Portugal; they are to be enjoyed mainly in Beira and Estremadura, especially at Cintra and Coimbra, and in the northern provinces. In the deep valleys where the mountains keep off the cool winds, it is excessively hot in summer; while on the summits of the mountains snow lies for many months. The meteorological station on the Serra da Estrella, with a mean annual temperature of 44-7° F., is the coldest spot in Portugal in which systematic observations are taken. Montalegre has a mean of 48-3° and Guarda of 5o~ 3°. Even in Lisbon the yearly variation is not less than 5o°. In Alemtejo the climate is Very unfavourable, and, though the heat is not so great as in Algarve (where Lagos has a mean of 63°), the country has a more deserted appearance; while in winter when the Tagus overflows, unhealthy swamps are left. Notwithstanding that Algarve is hotter than Alemtejo, a profuse vegetation takes away much of the tropical effect. Portugal is very rarely visited by' thunderstorms; but shocks of earthquake are frequently felt, and recall the great earthquake of Lisbon (q.v.) in 1755.

Fauna and Flora.-An, account of the fauna of the Iberian Peninsula as a whole is given under SPAIN. Wolves are found in the wilder parts of the Serra da Estrella, and wild boars are preserved in some districts. As far as the constituents of its flora are concerned Portugal is not very dissimilar from Spain, but their distribution is peculiar. The vegetation of Spain is distributed in clearly marked zones; but over the whole of Portugal, except the hottest parts of Algarve and Alemtejo, the plants of northern Europe flourish side by side with cacti, palms, aloes and tree-ferns (see CINTRA). This is largely due to the fact "that the moisture laden winds from the Atlantic penetrate almost as far inland as the Portuguese frontier, but do not reach the interior of Spain. The soil is fertile, and the indigenous flora has been greatly enriched by the importation of such plants as the agave, the Mexican opuntia, the American maple, the Australian eucalyptus, the Scotch fir and the so-called Portuguese cypress (Cupressus lusitanica) from the Azores. There are many fine tracts of forest, among which ma; be mentioned the famous convent-wood of Bussaco (q.v.); cor