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Plots and mares

The salt pans are a complex system of reservoirs (plots), channels and tanks for the decantation and evaporation of salty water. They are separated by dykes and slopes colonized by typical marsh vegetation, for the extraction of salt.

The lower estuary of the Lima River is a wide depression, with easily flooded river banks although with different frequency. Running the Lima River embedded in the Lima fault (ENE-WSW), its banks have different reference altitudes: to the north, higher (2.6 to 3 m above sea level) where the salt pans of Meadela are found, and to the south, lower (0.1 to 2.3 m above sea level) where the salt pans of Darque are found. It is precisely for this reason that the wetlands S. Simão and the lagoons of Vila Franca appear on this shore, and the salt production is less important than on the northern shore, as it is more difficult to guarantee the necessary conditions for water evaporation.

The Lima River estuary, was considered the “largest salt center of the Minho coast”. Salt being one of the most precious goods, “it was of great importance to own salt pans, which even reached prohibitive prices, as is the case of two plots in Darque that were exchanged in 1085 for a mare.


References:

Almeida, C. B. (2005). A exploração do sal na costa portuguesa a Norte do Rio Ave. In: Da Antiguidade Clássica à Baixa Idade Média. Actas do I Seminário Internacional sobre o sal português. Instituto de História Moderna da Universidade do Porto, Porto, p. 137-170

Carvalhido (2012). O Litoral Norte de Portugal (Minho-Neiva): evolução paleoambiental quaternária e proposta de conservação do património geomorfológico. Tese de Doutoramento, Universidade do Minho, 560 p.

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Gone with the wind

The formation of dunes by the wind

Dunes are landforms that develop from the movement of sedimentary particles driven by a fluid, usually air or water (esq. A).

The transport of sediments leads to the formation of rhythmic elevations with two faces. The windward face is less inclined and the opposite face is more inclined. The crest of the dune separates its two faces. Sediments are moved from the windward face to the opposite face. This continued action results in the dune migrating in the same direction of the prevailing wind. This migration continues as long as: i) the wind continues to blow; ii) there is enough supply of sand and; iii) there are no obstacles in the way the dune is migrating.

Types of dunes

Regarding morphology, dunes may be classified into six major groups, based on the shape, number of faces, and wind direction (esq. B).

Transverse dunes form when there is plenty of sand. Viewed from above, these dunes have parallel or slightly curved ridges and align perpendicular to the prevailing wind direction. There is a close relationship between the height of the dune, its width and the space between ridges. The transverse dune sediments give rise to a cross bedding that is preserved at the same time as the dune migrates. Transverse dunes account for about 40% of existing dunes globally.

Linear dunes are formed in areas with limited sediment supply but strong wind. The elongated parts of these dunes are parallel to the wind direction. These dunes are usually less than 4 meters high, but can extend for several kilometres. In the wide deserts, for example, these dunes can reach 100m in height and 120km long.

Barchan dunes are formed in the absence of vegetation, with dominant wind with slight variations and limited sediment input. Barcans occur as isolated, crescent-shaped dunes with a well-marked concave face and horn-shaped tips that develop to leeward. If wind conditions are relatively constant, they can migrate long distances without significant changes in shape. Most barcans have a convex profile and their height is typically 1/10 of their width. If the sediment input increases progressively, the dunes barcans can progressively form barcanoid dunes or even transverse dunes. As in the transverse dunes, barcanoid dunes also give rise to cross-bedding. Barcans represent only a small percentage of dunes globally.

Parabolic dunes are common in most low coastal areas and sandy environments in semi-arid environments. Parabolic dunes are characterized by the U-shape in which the ends or tails of the dune that lie behind are parallel and partially overgrown. The most frontal part, also called the “nose” of the dune, advances further than these points. The conditions of formation of these dunes are not yet fully understood, but seem to be associated with the presence of moderately developed vegetation, a strong and predominantly unidirectional wind regime, and a reasonable sediment input. The parabolic dunes are reminiscent of the barcans dunes but with the ends pointing in the opposite direction. The dune can be anchored by vegetation.

Star dunes are characterized by their considerable size, in the order of hectares, pyramidal shape and radiant and curved tips or arms. The basal faces of the star dunes consist of a smooth and wide profile. They are the largest dunes in many deserts and can reach heights of over 300 meters. They usually have a higher volume of sand than other types of dune. These dunes are associated with locations with high sediment availability and varying wind directions, especially at the time of transport. They have a central peak with a pyramidal shape, from which radially extend several tips or arms, the whole having several faces.

In what concerns its mobility, dunes can be stationary or migratory. In stationary dunes, the sand settles in successive layers that follow the exposed profile of the dune, creating a stratified internal structure. Although, downwind of the dune, strong wind-generated turbulence may occur, the sand particles remain attached to the windward strata, which tends to block the movement of the dune. Increasing moisture, internal obstacles (rocky outcrops, logs, etc.), or vegetation may affect dune mobility.

In the migratory dunes, sediments move downwind and precipitate downwind, leading to dune migration. The intensity of this movement varies, depending on the intensity of the wind, the availability of sediment, the existence of obstacles, among others. Dune migration can cause problems, such as infilling of water bodies or burial of agricultural fields or built structures.

Fossil dunes are consolidated dunes or paleodunes, and represent a development stage after the dune formation and mobility. This process may be short, corresponding to the consolidation of dunes due to absence of wind or water or by protection of the dune sediment by vegetation. In more advanced stages, which may last several thousand years, dune consolidation may occur, but maintaining the respective sedimentary structures. Such consolidation may be due to the formation of a carbonate cement resulting, for example, from the dissolution of fragments of shell constituents of the sand or from the percolation of carbonates carried by water.

In Galeão hill there are four steps at 50 m (Vila Fria step), 75 m (Ola step), 100 m (Faro de Anha step) and 160 m high (Além do Rio step). Between the 16th and 19th centuries, a colder climate and the absence of vegetation allowed the sand to spread until the top of Galeão hill (esq. C).

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Climbing Dunes in Faro de Anha

The Local Natural Monument corresponds to the NE side of the Galeão massif (57 ha), located on the left bank of the mouth of the Lima River. In this area, three flattening surfaces are preserved: Vila Fria Surface (50 m), Ola Surface (75 m) and Faro de Anha Surface (100 m) (Carvalhido, 2012; Carvalhido, 2014a, 2014b, 2014c). These surfaces are regularized by sandy deposits, well calibrated, preserving interlaced stratification and cross lamination by current ripples (Carvalhido, 2012, 2014a, 2014b, 2014c, 2014d).

The Areias de Galeão are dune sands deposited at the culmination of the climate crisis of the Little Ice Age (Dalton Minimum) (radiometric dating indicates deposition between the years 1780 and 1800). The typical criss-cross stratification of this unit is clear in some sectors, although sometimes only low-angle beams are observed (Carvalhido, 2012, 2014d). The morphometry and morphoscopy data prove the aeolic origin of the deposits, consisting of grains from rolled to sub-rolled features, with perforated and shiny rounded surfaces. The low humidity conditions, associated with the strong winds that would have been felt during the Dalton Minimum, will have been responsible for the transport and subsequent wind regulation of the Galeão surfaces. Despite the carbonated content of Areias de Galeão, the recent age, the weak thickness of the deposits and the cold conditions (conducive to the dissolution of carbonates) will have prevented their consolidation. Parish memories are an asset with potential for exploring this theme (e.g. disappearance of the parish of Aster under the dune sands). The base of the Areias de Galeão unit (first 20 cm) conserves medium to fine granite clasts, of two micas and biotitic (MPS = 20 cm), subangular (Carvalhido, 2012).

Under the dune sands there is the lithostratigraphic unit Areias da Ribeira da Areia, which corresponds to the water availability conditions that precede the Maunder Minimum, which constitutes the period of full installation of the Little Ice Age in Europe. The standard deposits retain some of the sets of frontal ripples with preserved internal structure - tangential to sigmoidal frontal blades, inclined towards NE and dorsal counterflow blades. The OSL dating of the deposits revealed installation between the years 1590 to 1650 (Carvalhido, 2012, 2014c).

The available radiometric data, the stratigraphic contact in involution and the decacentimetric clasts of medium grain granite, of 2 micas, angular, in the transition between the two levels, allow to deduce the association of the deposits with climatic evolution until the installation of the Maunder Minimum: the lower level is associated with a medium with available liquid water, associated with currents (Areias da Ribeira da Areia), to degrade the wind deposits at higher levels, later transitioning to cold conditions (signs of cryoturbation in the transition between both units), strong winds but not very humid (Maunder Minimum) (Areias de Galeão) (Carvalhido, 2012).


References:

Carvalhido (2012). O Litoral Norte de Portugal (Minho-Neiva): evolução paleoambiental quaternária e proposta de conservação do património geomorfológico. Tese de Doutoramento, Universidade do Minho, 564 p.

Carvalhido, R.; Pereira, D. & Cunha, P. (2014a) – Depósitos costeiros quaternários do noroeste de Portugal (Minho - Neiva): caracterização datação e interpretação paleoambiental. Comunicações Geológicas (2014) 101, Especial II, 605–609.

Carvalhido, R.; Brilha, J. & Pereira, D. (2014b) – Monumentos Naturais Locais de Viana do Castelo: processo de classificação e estratégias de valorização. Comunicações Geológicas (2014) 101, Especial III, 1219–1223.

Carvalhido, R.; Pereira, D; Cunha, P.; Buylaert, J. & Murray, A. (2014c) Characterization and dating of coastal deposits of NW Portugal (Minho-Neiva area): a record of climate, eustasy and crustal uplift during the Quaternary. Quat Int, 328-329: 94–106

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PEQ2 - Lanheses-Montaria Equestrian Trail

Departing from the right bank of the Lima River, next to the pier where boats from the “lugar de passagem” (place of passage) once docked, this equestrian trail ascends the southern slope of the Arga mountain, towards the local village of Montaria.

The contrasting landscape along the approximate 13 km of the trail is distinct, reflecting mankind’s adaptation to disparate environmental conditions. If the somewhat flat areas of the valley fostered a dispersed settlement pattern, where only historically significant centres stand out, as is the case with Lanheses, as you ascend in altitude, you will notice that the scenery and terrain changes influencing the agglomeration of rural settlements and the farming systems.





Datasheet PEQ2 - Lanheses-Montaria Equestrian Trail

Duration: 4h00m

Distance: 13 km

Initial height: 3m

Minimum height: 290m

Maximum height: 3m

Difficulty level: Easy

Category: Linear

Starting point: 41.727306, -8.675678


Informative leaflet: PEQ 2 - PERCURSO EQUESTRE LANHESES - MONTARIA (SERRA DE ARGA)

Route in KMZ format for download: KMZ_PEQ2 PERCURSO EQUESTRE LANHESES - MONTARIA (SERRA DE ARGA)

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PR17 - Monte Galeão Trail

The Monte Galeão trail is a pedestrian short-distance trail (PR17 - Portuguese acronym), so the respective marking and signage obeys international standards. The numbering is assigned by the Municipality of Viana do Castelo. This route is located in the parish of Darque, in the municipality of Viana do Castelo. Very interesting little mountain trail, due to the fact that it crosses a patch of very varied vegetation and with stunning views over the Lima River and the city of Viana do Castelo.




Datasheet PR17 - Monte Galeão Trail

Duration: 2h00m

Distance: 2,43 km

Difficulty level: Moderate

Category: Circular

Starting point: 41.677647, -8.793583


Route in KMZ format for download: KMZ_PR17 TRILHO DO MONTE GALEAO

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Castro de Moldes

PR13 - Castro de Moldes Trail

The “Castro de Moldes” (Castro – a fortified settlement) trail is a short-distance walking trail (PR13-portuguese acronym), part of a network of walking trails in Viana do Castelo. These are marked trails with international symbols and each has been numbered by the municipality.

Located in the coastal village of Castelo do Neiva, in the municipality of Viana do Castelo, this trail takes visitors through some incredibly scenic areas where you may admire the beauty of nature, cultural heritage sites and archaeological remains. In addition to the unique landscapes over the river, the sea and the mountain that this trail offers, there are also signs of religiosity in the little shrines, cruises, chapels and the connection to the Portuguese Coastal route of El Camino de Santiago (Way of Saint James); the Palheiros de Sargaço (Seaweed Shacks); watermills, “Penedo das Chaves”; Castro de Moldes (fortified settlement); the Sebastião Bridge and the Parish Church.



Datasheet PR13 - Castro de Moldes Trail

Duration: 4h00m

Distance: 11,35 km

Difficulty level: Easy

Category: Circular

Starting point: 41.623869, -8.795128


Route in KMZ format for download: KMZ_PR13 TRILHO CASTRO DE MOLDES

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Moinho do Marinheiro

Marinheiro windmill

It is the only mill of wooden trapezoidal sails that still works, since it was acquired and recovered by the City Council in 2002, continuing to grind corn grain. This mill was built in 1877 and is classified as a property of public interest.

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Dia Mundial do Ambiente em Viana do Castelo assinala primeiro aniversário sobre abertura livre do Parque Ecológico Urbano

O Parque Ecológico Urbano, que reabriu há precisamente um ano em formato de acesso livre, foi hoje palco de um conjunto de iniciativas no âmbito […]
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TrailGazers: a primeira reunião cara-a-cara do comité do projeto desde 2019 teve lugar em La Palma

No passado dia 3 de maio a Divisão de Ambiente e Sustentabilidade do Município de Viana do Castelo, participou remotamente na primeira reunião presencial do […]
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“Viana Florida” decora cidade com 40 mil flores e oferece feira de flores, exposição e animação variada

Até dia 15 de maio, Viana do Castelo volta a ser palco da iniciativa “Viana Florida”. Para celebrar todos os motivos florais que distinguem e […]
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