Geography – Physical Characteristics

Topography and characteristics of the area

Maximum height: 1215 m in the Mountain Range of Oribio.

Minimum height: 100 m in the Eastern ledges of the Mountain Range of Xistral.

For more information see Topographical Plan.

Altitudes (m)Area (ha)%
75-100172,80,0
100-200354,10,1
200-300764,70,2
300-40021156,75,8
400-500157099,143,2
500-600105157,828,9
600-70047566,413,1
700-80020186,55,6
800-9008109,12,2
900-10002506,50,7
1000-1100450,10,1
1100-1200143,40,0
1200-13001,60,0
TOTAL363668,8100.0

In the territory Terras do Miño two of the main geomorphologic units of Galicia can be distinguished:

  1. The plateau of Lugo
  2. 2The northern ranges.

The plateau of Lugo constitutes a low-lying zone, slightly sunken in relation to the less defined orography which surrounds it. In it four subunits can be distinguished:

  • he mountain ledges which act as eastern and western borders,
  • the levelling forms or plateaus at different levels,
  • the tertiary sunken areas
  • and the river valleys which fit in the whole and that contribute to fragment the levelling areas.

The mountain ledges. The plateau or plateau is delimited in its northern part by the northern ranges and a more heterogeneous set of mountains, amongst which the hill range of Neda and A Corda stands out. (See topographical plan)

To the east, the limit is marked by the first alignments which constitute the whole of the eastern ranges of Lugo, oriented north-south, in general (Range of Pousadoiro, Range of Meira, Range of Mirador, Range of Vaqueriza and the Range of Oribio).

To the west, the divide is formed by the most northern branch of the so called Galician western ridge, formed by a set of ranges oriented north-south and whose range line continues, in general terms, the current administrative limit between the provinces of Lugo and A Coruña. These ranges (Range of Loba, Hill Range of Montouto, Range of Cova da Serpe, Range of Careón and Range of Farelo) constitute the divide of waters between the sources of the tributaries of the Miño, on the one hand, and the rivers that flow directly into the Atlantic (Mandeo, Tambre, etc.).

All these ranges owe their fundamental route to tectonics, regardless of the materials which predominate in each of them and have, in general, levelled peaks due to erosion.

The levelling areas. They are formed by extensive erosion areas, elaborated throughout the Tertiary on ancient materials, and slightly tilted in an ascending direction facing south. This levelled zones predominate in the studied area, hence the name of the plateau of Lugo.

The first level, situated between 540 and 580 m, occupies the towns of Xermade and Guitiriz, lengthened to the south occupying the towns of Friol, Begonte, Outeiro de Rei and Lugo, and extended towards the eastern ranges until the towns of Castroverde, Castro de Rei and Pol. This level comes into contact with another placed in a lower altitude, at around 450 m, located in the western part of Terra Chá.

In the proximities of the eastern ranges another high flattened level can be distinguished, at around 700 m of altitude, next to Meira, lengthening in a discontinuous fashion until the sunken area of Sarria.

When they approach the southern border of the basin, the levelling areas elevate until they almost reach 600 m, in the towns of Guntín, Láncara and O Páramo. The progressive fitting of the Miño river is a test to this tilting process.

The tertiary hollows are more or less extensive areas that have in common an inferior altitude –in the context of the levelling areas—, the flat or almost flat topography, and the recent sedimentary materials which form them.

Examples of these areas are the BRAÑA of Boedo, in Guitiriz, and the basin of Roupar to the northwest, covered by alluvial deposits; the eastern part of Terra Chá, located at 400-420 m, characterised by the presence of difficult draining materials and the abundance of small lakes (Bardancos and Cospeito).

The river valleys. This subunit of the plateau of Lugo is formed by the numerous water courses which form the high basin of the Miño river. These helped degrade the different levels of the flat areas, tracing light slopes and little deep valleys, wandering without hardly fitting into the tertiary depressions and fitting more and more as they approach the south of the basin.

The southern mountain ranges appear represented in the area of study because of the foothills of the Range of Carba (905 m) and especially because of the Range of Xistral; these set the water divide between the Cantabrian rivers and the high basin of the Miño.

The Range of Xistral, located in the central heart of the southern ranges, is comprised of a whole of minor ranges following a NNE-SSW direction and in which the highest peaks of O Cadramón (1060 m), Seixo Branco (1057 m), Chan do Lamoso (1039 m), Xistral (1036 m) and Lombo Pequeño (1015 m) are reached.

It is characterised by an abrupt relief whose configuration is due to the lithological differentiation (presence of schists, slates, quartzite...), the river action, the tectonic dynamics and the climate changes, amongst which the glacier and periglacial morphogenesis must be stood out. The tectonic dynamics affecting this range has also determined the existence of various systems of faults and fractures that, especially in granitic areas, have conditioned to a great extent the installation of the river network and the valleys.

It stands out the presence of different ways the granitic zones are modelled.

As ways of exhumation present, we can mention (DÍAZ VARELA, 1999): “botos”, tors, castle kopjes, domes and microforms. On the other hand, some areas have been recognised where alteration alveolus appear, as well as mosaics of ways of exhumation with alteration alveolus.

The glacier and periglacial geomorphological processes are the ones that have influenced the morphogenesis of the relief of southern mountains the most. Then, the presence of elements of the glacier and river glacier stands out (cirques, valleys with flat bottoms and Moraine-dammed summits); as well as elements of the periglacial modelling (regularised slopes, slopes in blocks and rock glaciers).

The hydrological and fluvial modelling is represented with the presence of ponds, subsidences, canyons, fluvial terraces, ejecta cones and enclosed fluvial valleys.

Moreover, most of the Range of Xistral appears covered by a blanket of sediments of variable power from different sources. In the Range of Xistral several types of surface features have been recognised: glacial and fluvioglacial deposits (moraines, fluvioglacial terraces, till), periglacial deposits (block slopes, rock glaciers, debris, flows of cold water), fluvial deposits (fluvial terraces, ejecta cones) and organic deposits of great importance, such as peatlands. In these mountains according to the criteria by RAMIL REGO et al. (1996), the following types of peatlands have been distinguished: blanket bogs, raised bogs of alveoli, high bogs of valley bottoms, hillside bogs and raised bogs of glacier shutter.

The hydro-graphic network

The proposed area includes most of the Upper Miño river from its source to the confluence with the Ferreira River, in the tail of the reservoir of Portomarín. It covers an area of 3,321 km2, over 90% of the territory proposed as a Biosphere Reserve, and 28% of the total area of the basin of the river Miño. It is limited to the north by the northern mountains, to the west by the Galician ridge and to the east by the Eastern ranges, as described above.

The Miño, according to most authors, has its source in the Range of Meira, in the place known as Pedregal of Irimia at 700 m altitude, from which a spring emerges, constantly flowing from blocks of Ordovician quartzites devoid of vegetation which results in a very distinctive landscape. See topographical map.

Following geographical criteria (IZCO, 1997), the sources of Miño are in the Galician-Asturian Massif (Range of Carba, Range of Xistral, Range of Toxiza, etc.), where the northernmost reaches of the Miño are formed; the stream Casal, at the foot of Monte Peñote Pena Goia and the stream Labrada, on the slopes of Pena da Mosa.

The various streams and channels formed in the southern slopes of the Galician-Asturian Massif finally converge forming the channels of Trimaz, Madalena, Batan, Arnela, Anllo, Labrada, etc.

Following the course of the river from the Pedregal of Irimia, this gradually thickens with two brooks: Porto da Pena and Xirómeno to form a defined channel. After the village of Meira, 6 km from its origin receives on the left the flow of the Lagoa de Fonmiñá. This gap, commonly regarded as the birth of Miño, is a karst emergence caused by the existence of two calcareous bands crossing the area of Fonmiñá from north to south.

From this point on the Miño runs on its floods in the Terra Chá. Its course is tamed and rambling for the next 50 km, in which only falls by 0.19% (RIVER BARJA et al., 1992), it is then that its course becomes extremely rambling, changing course repeatedly, opening in various arms, forming anastomosing channels and islands or endorheic lagoons. From Fonmiñá, Miño takes a NW course and receives the tributaries of Madalena or Miñotelo and Rigueira or Úbeda on its left bank.

From Úbeda, Miño takes a SW course entering the depression known as As Lamas, lakeside area formed by sediments which receives the river Pequeno on its right, after flowing in parallel for 8 Km. Two tributaries of the River Pequeno, the Fontadrao and the Pontiga, of more than 5 km in length are subsumed in the Terra Chá at the parish of Muimenta.

Later, it encounters the river Azúmara, coming from the mountain ranges of Monciro and Mirador, after it flows for 25 Km.

The next river that joins the Miño is the Anllo: it is born in the foothills of the Range of Carba and in its first few miles forges a deep valley, looking more like the Cantabrian rivers to the ones in Terra Chá, but recovers from them the meandering flow of these rivers and breaks into two branches, the western branch, called Guisande river, to the lagoon of Cospeito and the one to the east which flows into the Miño. From this point, the Miño takes a SW course and receives the river Lea.

Downstream, it receives the river Támoga from its right, 25 km long, consisting of three arms: Santavalla, Arnela and Ribeira, which runs alongside the lagoon of Cospeito, which it drains.

The Lagoon of Cospeito is the most important testimony of a large endorheic area covering the entire bottom of the depression of Terra Chá, from which we can deduce that it could have been a lake in the Neogene by the lake nature of its sediments (RIO BARJA et al.,1992), which made its way to the sea through the Támoga-Miño. This lagoon was subject to colonization and land revaluation, for which it was dried. Subsequently, many restoration projects, that continue today, have been undertaken.

From the river Támoga, and before reaching Rábade, the river Miño takes a southerly direction and bifurcates originating the Ínsua of San Roque (106 ha), the largest of its entire length, formed by Tertiary sediments of lacustrine clays. Once past the island, the river Ladra joins the Miño, river that drains the entire western part of Terra Chá. This river is the main tributary regarding the area drained: 889 km2, followed closely by Neira: 832 Km2. Born in the Chaos of Roupar, where it is called river Trimaz. This river runs through this depression parallel to river Chamoselo, basin of the Eume, until one goes to the north and one to the south, without any capture process. At the confluence with Madalena, Trimaz and takes its name from the river Ladra, which still meets the rivers Parga and Labrada on its right before it flows into the Miño, after travelling 50 Km.

The Miño, before reaching Lugo, meets the river Robra from the right and the rivers Narla and Mera from the left. Back in the city of Lugo, ends the geographical and morphological unit of Terra Chá, having travelled the Miño until reaching this city 73 km with an average gradient of 0.45 % but, given its route only from Fonmiñá the slope is only 0.19% reflecting its rambling nature.

From Lugo onwards, it enters a new stage, in a new erosive cycle: the river, before rambling and quiet, now acquires a more dynamic nature opening an increasingly narrow channel from 40 m of height difference the water and the main flattening area in Martul and Robra, to 70 m in Lugo. From here to the south, as the level of critical erosion goes up, the river falls more into the same: in the limit of the municipality of Lugo reaches 100 m and reaches 200 m in Portomarín.

Following its course the Miño receives the river Chamoso from the left, and then, the second largest tributary in the basin area: the river Neira.

The river Neira emerges in Fontaneira at 940 m altitude. It has its first tributaries rather embedded in the Range of Portela until it reaches the valley Neira de Rei. It receives from the right the river Tórdea and from the left the Sarria, narrowing again when it meets this river. When it flows into the Miño, after travelling 54.5 km long, it reaches a height difference of 60-80 m.

Finally, near the right bank next to the limit of the area at hand, the river Ferreira discharges. This river is born in the Range of Careón at 700 m altitude, it receives the small river of Lavadoiro and, after 42 Km, it flows into the Miño.

The area proposed as a biosphere reserve comprises mostly the upper reaches of the river Miño (more than 90% of the total area), but in this area we can find the sources of four more rivers in the summits of Xistral. They are the Eume, Landro, Ouro and Masma rivers, which together account for 8% of the total area.