[11] The highland rim extending continuously from the eastern Pyrenees across northern Spain and southward into northern Portugal has a distinct physical character and, through its effect upon climate, creates a distinct character for the meseta. The surface form of the great central tableland is relatively simple and for the purposes of this study need not concern us. The landforms of the northwest, however, especially those in the north of present Portugal, must be considered in some detail, for this area is pertinent to our problem.

The most important fact of North Portuguese landform is its seaward slope. This orientation is most obvious in the province of the Minho, where mountains to the east (the Peneda, Gerez, Cabreira, Alvão, Marão, and Montemuro) form an amphitheater facing the Atlantic Ocean (Fig. 3. See Fig. 1 for additional place names). Such heights allow northwest [12] Portugal to turn its back upon the meseta of Spain. Due not only to their elevation but also to their geologic and tectonic history, they represent an area of limited usefulness and sparse population. Here events of nearly three hundred million years ago cast their shadow upon present human affairs. The general area is one of Hercynian folding, which resulted not only in the metamorphosis of existing rocks but also in great intrusions of granite. ⁽¹⁾ Late Tertiary re-elevation and subsequent erosion resulted in the complete exposure of the ancient crystallines and granites along a line making a gentle arc, convex toward the sea, from near La Coruña, running south-southeastward through the areas of Vila Real and Guarda in Portugal and into Spain near Alcántara. It is also a zone of shatter breaks marked by lines of thermal springs, especially in the granites.

In this part of Iberia, geology has no relation to the political boundary. A granite massif extends from the west border of Asturias through Galicia and thence southward through the province of the Minho. South of the Douro River it is buried along the coast by later (post-Paleozoic) sediments, but inland it continues as a surface feature almost to the city of Coimbra. This massif in Galicia forms an amorphous mass, but its projections extending into Portugal take clear form as crests roughly parallel to each other, running in a south-southwest direction (Peneda, Gerez, Alturas, Alvão). The Minhotos call these collectively as Montanhas (the Mountains), one of the subdivisions that they make of their province. Paralleling these ridges, the rivers run in their deeply trenched valleys, the Lima, the [14] Cávado, the Homem, and the Tâmega. A typical phenomenon of the Minho Province is that of a broad, flat valley floor lying sharply against steep bordering slopes. The form and the parallelism of the valleys suggest tectonic derivation -- and the horsts of Marao and Padrela at the eastern edge seem to confirm it -- but the genesis is largely of another sort. The forms are simply the result of the typical erosional development of granite in northwest Portugal. Here, either along fault lines or in rejuvenated valleys the process of river erosion widens the floor without reducing the angle of slopes, which recede parallel to their earlier position. ⁽²⁾

Seaward from the granite crests is an area of low valleys, called o Centro (the Center), irregular in shape and size and partially enclosed by granite spurs. It is a fertile area of dense settlement and the core of Portuguese nationality. The Coast is the third division which a Minhoto makes of his province. It is an emergent coast, with a narrow beach sloping gradually upward to the slight eminences just a few miles inland, against which the waves of the Pliocene sea washed.
 

The Minho shares with its eastern neighboring province the mountains described above. These heights form the physical division -- topographic and climatic, with all that this implies in human terms -- between the green Minho Province and its eastern neighbor, the aptly named province of Tràs-os-Montes. ⁽³⁾ The latter, lying in the lee of the mountains, in the northeast of Portugal, is bordered on two sides by Spain and physically is an extension of the Spanish meseta. However, it has characteristics peculiarly its own. Unlike the Spanish peneplane with its low relief and Tertiary cover, the high, partly dissected [16] plateau on the Portuguese side of the border is constituted largely by Pre-Cambrian materials, and is deeply incised by its rivers, which have carved canyons up to sixteen hundred feet deep into the ancient crystalline rocks. In addition to this difference in the effect of the rivers, there is the feature of unreduced remnants of former elevations, which project high above the peneplane surface on the Portuguese side of the border.
 

The Spanish Duero flows lazily westward to beyond Zamora; and its tributaries, also leisurely streams, come into it from the east-southeast or from the northwest. At Paradela, where it becomes international (the Douro, in Portugal), ⁽⁴⁾ it suddenly bends to the southwest, cutting violently into the old plateau surface, dropping over sixteen hundred feet during the next seventy-six miles. To the west of the canyon, the right bank [19] tributaries in Tràs-os-Montes roughly parallel the international stream, and are separated from each other by northeast-southwest trending crests. This change in direction and degree of slope of mountains and rivers is a phenomenon of the zone of northeast Portugal that borders León.

Because of the position of the highland areas, most of the streams of Portugal north of the Douro are purely Portuguese streams. There is an important Spanish section of the Minho River (Miño, in Spain) , which has its sources in the northern mountains of Galicia. The Lima ( Limia, in Spain) River runs for approximately half of its course in southern Galicia and enters Portugal through the sharply cut canyon between the serras of Peneda and Amarela. The Tâmega also has a portion of its course in Galicia, in the region of the town of Verin. This stretch, however, is but a few miles long and is separated from the rest of Galicia by relatively high country. Aside from these three streams, all others have their sources either within Portugal or on the south slope of the mountains along the frontier. The valleys of the streams are narrow and of limited, if any, usefulness near their headwaters, but they widen downstream.

The fact that all of the Tràs-os-Montes streams cut deep canyons into the old plateau surface is not only of physiographic but also of economic and political significance, for these valley bottoms, where they are wide enough for use, with advantageous climatic conditions, are ribbons of fertility in an otherwise meagre territory. Their topographic gradient is also their economic and political gradient. Routes to the west are open, whereas all are blocked to the east and north, either by high mountains or by narrow canyons, where the turbulent streams make navigation impossible and where cultivable land is absent (e.g., the Douro between Paradela and Barca d'Alva, and the international Maçãs, in Spain, the Manzanas). The economic current, by reason of these facts, is westward, away from the Spanish border and toward the Portuguese lowland.
 

[21] The rocks and landforms of the Minho extend southward beyond the Douro River to a point north of the city of Coimbra, where the granite Caramulo, whose northeast-southwest strike is that of its counterparts in the northern province, marks their termination. This brings the rocks and landforms of the Mountains of the Minho Province well into the drainage of the Mondego River of Middle Portugal. However, not only the Mountains of the Minho extend south of the Douro River; the Center of the Minho also is extended recognizably as the low mountain-girt valleys of the Beiras; and a short stretch of coast to the south of the Douro River is a southern extension of the Coast of the Minho.

Most of Middle Portugal is included in the Beira provinces, so named (Beira means border) because the lands south of the Douro River were frontiers during the period of reconquest and resettlement (ninth to twelfth centuries) which stemmed from the early Portuguese nucleus in the Minho. Likewise, they form the frontier of Trás-os-Montes, and here also one can recognize a southern companion-piece to the northern province. The heart of Upper Beira (that part of the Beiras lying to the northwest of the great dividing range, the Serra da Estrêla) is an elevated plain, partly dissected by the streams of the Mondego system. Although the carving of the streams has been vigorous, it has not destroyed the essential unity of interfluvial surfaces. Like Trás-os-Montes, this high plain is an extension of the meseta of Old Castile. Also, like its northern neighbor, it differs from the Spanish area in the form of its stream valleys.

The Agueda River, a left-bank tributary of the Duero, takes its northwesterly course through the high plateau of Old Castile in leisurely fashion, comparable to that of the Spanish Duero. At the frontier it has cut an even steeper gradient than the Duero into the ancient rocks before the two streams meet above Barca d'Alva. (In fifteen miles the Agueda drops nearly [22] eight hundred feet for an average decline of approximately fifty-two feet per mile compared with twenty-one feet per mile for the international Duero.) The valley of the Côa River, another left-bank tributary of the Douro River, is called terra quente (hot country) by the Portuguese, a term used to describe such low, protected valleys which are favored by climatic conditions so different from those of the high plateau directly above them. The term is applied equally to the valley of the Sabor River in Trás-os-Montes, due north of the Côa, and to several others in each province. Most streams of the Beira meet the Douro in an acute angle as do those from the north. The exceptions on either side of the master-stream seem to be those directed by tectonics. For example, the Ca and its northern companion-piece, the Vilariça, tributary of the Sabor, flow almost due north and south respectively along fault lines. The high plain of the Beiras extends westward until it ends at the Bussaco Mountains, north-northeast of the city of Coimbra. On the northwest it is bounded by the mountains of Caramulo, Montemuro, and their extensions. On the southeast its boundary is the great fault line along which the Serra da Estrêla was raised.
 

The northeastern section of Upper Beira, sometimes termed Transmontane Beira, is like Trás-os-Montes not only in that it is distant from the ocean, but also in that the effect of oceanic influence is diminished because of the mountain masses west of it. The area includes the drainage of the Côa River. Farther south, this Portuguese extension of the Spanish meseta continues through the so-called Guarda Gate, lying to the east of the city of Guarda, a high, bleak plateau surface, averaging almost three thousand feet in elevation, between the Serra da Estrêla on the west and the Sierra de Gata and its Portuguese relative, the Serra das Mesas, on the east. The Guarda Gate, like its Spanish companions, the Gates of Béjar and Avila, connects, without major topographic obstacle, the ancient erosion surface of the north meseta with that of the south.
 

About fifteen miles south of the latitude of the city of Guarda is the water parting between the affluents of the Douro River at the north and those of the Tejo River ( Tajo, in Spain; Tagus, commonly on American and English maps) at the south. This divide is approximately at the northern boundary of the province of Lower Beira, most of which lies between the levels of sixteen hundred feet and seven hundred feet elevation. From its highest elevations, Lower Beira slopes southward to the Tejo River. As Upper Beira (or its eastern section known as Transmontane Beira) is a continuation of the plateau of Old Castile, Lower Beira is an extension into Portugal of Spanish New Castile; both provinces are transitional in character. Upper Beira reflects the traits of its nearest neighbors, the Minho and Trás-os-Montes, and Lower Beira shows strong affinities toward the Alentejo, into which it imperceptibly merges on the south. Castelo Branco of the Lower Beira is in many respects suggestive of an Alentejo city, and the countryside is similarly reminiscent.
 

Between the Mondego and the Transmontane Beira extensions of the ancient plateau, the great horst of the Serra da Estrêla has been thrust. This greatest Portuguese range has an average width of about thirty miles and a length of seventy-five miles. Here is found the highest point of the country (6,532 feet). This range, like the Serra das Mesas and the Spanish sierras of Gata, Gredos, and Guadarrama, was elevated along great fault lines in Middle Tertiary time. As the great so-called dividing ranges of Spain separate Old and New Castile, so does the Serra da Estrèla make an effective barrier between the northern and southern parts of Portugal. Only along the littoral on the west, or by the Guarda Gate on the east, is contact between them conveniently made.

The Serra da Estrèla is made up of a series of mesas, one set back above another, which have now mostly weathered into [24] high rounded eminences with but few sharp crests. The bounding fault along the northwest is clear, and, although there is still discussion as to the geologic and tectonic history of the other border areas, it is commonly accepted that the southeastern boundary also may be delimited along a series of fault scarps. On the northeast the slopes grade into the plain of Transmontane Beira and on the southwest the granites of the Estréla dip beneath the Triassic sandstones of Portuguese Estremadura.
 

Of all of the territory lying between the Douro and Tejo rivers only one important part can be said to be uniquely Portuguese and not a part of general Iberian landforms. This area lies to the west of a line drawn almost due north-south from Espinho through Coimbra to Tomar, and north of a line from Tomar to Lisbon. The area thus delimited includes virtually all of the modern provinces of Beira Littoral and Estremadura and has no companion-piece in Spain or north of the Douro in Portugal.

Its first and most obvious difference from the lands about which we have been speaking thus far is that of geologic age. It is a region in which the granites and schists, dominant in the north and in most of the center of Portugal, are totally lacking. Against these ancient rocks of the interior lies an almost continuous narrow band of Triassic sandstones reaching from Tomar, just north of the Tejo River to north of Coimbra and, discontinuously, as far north as the Vouga River. Westward and southwestward from these Triassic sandstones lies a broad band of limestones of Jurassic age, broken by considerable areas of Cretaceous sandstones and conglomerates. Still farther west, especially in the triangle bounded by a line drawn from Espinho to Coimbra and from there to Nazaré, are Tertiary layers, dipping on the seaward side under Quaternary deposits. Within these major, generalized rock areas are small enclaves of disparate character. For example, within the general zone [26] of Jurassic and Cretaceous rocks are many areas of eruptives, the most important of which is that of basalts just to the west and northwest of Lisbon. Within the Tertiary zone are several minor areas where Mesozoic rocks are exposed. The small Berlenga Islands, lying offshore to the west of Cape Carvoeiro, represent an isolated fragment of the ancient mass separated from the latter by the Mesozoic area.

The differences in resistance to weathering of the limestones, sandstones, and volcanic rocks has produced a region with great variety of form. Occasionally one sees sandy hills or hills of basalt, and calcareous eminences that do not reach more than 2,500 feet in elevation. These eminences are striking because of their abrupt, sometimes karstic, arid, desolate slopes. On the seaward border from the Douro River to the Mondego the coast is low and slopes gradually inland. Against the ocean is one of the greatest areas of dune sand of western Europe. Broken only by Cape Mondego (near Figueira da Foz), sands have been deposited as far south as Nazaré, stretching along for over a hundred miles and averaging two to five miles in width.
 

If one wanted to describe the Beiras in a single word he would use "variety," but for the neighboring region to the south only the word "monotony" would serve. There could hardly be greater contrast than that between the Beiras in general and the Alentejo, even though Lower Beira at the east makes an imperceptible transition into the Upper Alentejo. The two areas meet where ancient rocks have been modeled by erosion into rolling countryside, with an average elevation of seven hundred to sixteen hundred feet above sea level and sloping generally toward the west and the south. On the west, Lower Beira makes an abrupt transition into the lands to the south, along a series of faults presently reflected in the topography of the area. The adjacent southern area is the Ribatejo (a subdivision of Lower Alentejo), which is part of a great sedimentary basin making up the lower section of both the Tejo and Sado river [29] drainages, from which the sea withdrew in mid-Tertiary times. The Tertiary lands extend to the northwest of the river from ten to fifteen miles on the average, but to a far greater extent southward. There, its complex succession of continental sands, clays, and limestones are transgressive over the ancient rock as far as seventy-five miles south of the river, where the Tertiary materials meet the Carboniferous, sedimentary schists of the Lower Alentejo proper without a break in relief. The great level or gently undulating plain of the Lower Alentejo, largely under seven hundred feet in elevation, is a classic peneplain, with but a few widely separated crests of modest height breaking the monotony.
 

Toward its southern limit, the great plain of the Lower Alentejo slopes upward to form mountain ranges, the Caldeirão Mountains on the east and the schist matrix of the Monchique Mountains on the west The upfold of the schists resulted in faults normal to the fold, that is, somewhat parallel to the south coast of Portugal The southern slopes of the mountains are rugged areas of the unconformable meeting of schists with the Mesozoic strata of the Algarve The highest peak of the Caldeirão (Mú) is only 1,893 feet above sea level, but Monchique is a unique phenomenon, for there a laccolith of syenite has been exposed by erosion of the schists that formerly covered it. Being more resistant to erosion than its matrix, the syenite now towers nearly thirteen hundred feet above the highest crests of the schist (syenite Foia, 2,959 feet) around it.

These southern Portuguese mountains represent a purely Portuguese phenomenon, as they have no counterpart beyond the Portuguese boundary. Separating the two mountain areas is the Depression of S. Marcos, which represents a southern extension of the plain of Lower Alentejo. To the west of the Depression is a northwest-southeast trending fault, marking the eastern edge of the Monchique Mass. From the eastern side of the Depression the rise is gradual to the crests of the Caldeirão. [30] Another extension of the Alentejo surface is that to the west of the mountains of Monchique, where the plain surface, veneered by sands, can be identified along the Atlantic coast almost to the southern extremity of Portugal. A third extension lies to the east of the Caldeirão, where the Guadiana River has carved its course through a southern projection of the plain which reaches virtually to the southern sea coast.

The most southern political province of Portugal is named the Algarve. It includes the mountains of Caldeirão and Monchique, but this is a political device and not the expression of either the people inhabiting the mountains nor those of the lowlands beyond. A mountain man speaks of the Algarve, meaning the limestone and littoral area of the extreme south, and the Algarvian proper speaks of the mountaineers who inhabit the schist uplands.

Several faults mark the approximate line of division between the schists of the mountains and the Mesozoic measures of the Algarve proper. Some of these faults have a northwest-southeast direction and some run almost due west-east. Along the edge of the schists, almost all of the way across the country, is seen an exposure of a steeply dipping deposit of red continental sandstones, conglomerates, and marls of the Triassic. To the south of the Triassic band are thick, hard beds of Dolomite and compact limestones of the Lower Jurassic, forming high crests separated by lowlands scoured out of softer marls. Southward are successively younger and generally softer beds, where the relief becomes one of crests (generally in east-west direction) diminishing in height, and rough slopes separated by increasingly broad valleys, excavated by streams where the limestones are softer. South of the Mesozoic area is the littoral of Late Tertiary deposits, including marine limestones of the Miocene, and sands, gravels, and clays of Pliocene to recent time. The littoral slopes from the sea edge to elevations of as much as four hundred feet.

[31] It is easily apparent that Portugal, small though it is, is a place of physical diversity. Only the Beira provinces of the center show a considerable number of common characteristics. This has long been recognized by their being grouped together as ôthe Beiras.ö No one knowing the Minho, Trás-os-Montes, the Alentejo, and the Algarve, however, could think of them except as places with distinct physical character, each unlike the others.
 

1. In this chapter I have used material from the works of Hermann Lautensach: 1. "A Individualidade geográfica de Portugalno conjunto da Península Ibérica," Boletim da Sociedade de Geografia de Lisboa, XLIX (1931); "Portugal: Auf Grund eigener Reisen und der Literatur." 1. "Das Land als Ganzes," Petermann's Mitteilungen, No. 213 (Gotha, 1932); 2. "Die portugiesischen Landschaften," ibid., No 230 (Gotha, 1937).

I have also made use of materials from Orlando Ribero, Portugal; from A. de Amorim Girão, Geografia de Portugal; from Pierre Birot, Le Portugal; and from Mariano Feio, A Evolução do relevo do baixo Alentejo e Algarve.

2. Orlando Ribeiro, Portugal, pp. 19-23, 31.

3. That is, "on the other side of the mountains." The name properly implies the history of the province with regard to the earlier establishment of the Minho as a political center and the later adherence of Trás-os-Montes.

4. For the international streams both the Portuguese and the Spanish names will be given in the first reference. In subsequent references the spelling will be suited to the area under discussion.