XREI page dedicated to all maps of Portugal. Not all maps are listed here yet, but we add more as time allows. Bookmark this page if you want to learn about Portugal, because we are constantly building new features. From here you can also visit the Homes for sale in Portugal page, updated several times per week, and the Real Estate Developments in Portugal page.
Interactive Map of Portugal
This map also sits at the bottom of the Portugal article. Click any area to go deeper into each place, parish, municipality or district. Share it with people who care about Portugal.
What Portugal Is Made Of
The map paints every rock type a different colour. That is why Portugal looks striped. Each stripe is a different age and a different kind of ground. Below is a plain reading of the nine colours you see most.
| Rock | Where you see it | What it means on the ground |
|---|---|---|
| Granite and syenite | Minho, Trás-os-Montes, the Beiras, Serra da Estrela, the core of Serra de Sintra, Serra de Monchique | Hard rock and strong ground. Soil is thin and acid. Wells depend on cracks in the rock, so one plot can give water and the next one nothing. National radon mapping links high radon susceptibility to granite and syenite ground. The reference level is 300 Bq/m³ and only a test in the building itself gives a real number. The rock of Monchique is nepheline syenite, called foyaite after the peak of Fóia, which is the place the rock is named from. |
| Basalt and volcanic rock | Around Lisbon and Mafra, and around Sines | Old lava flows, roughly 72 million years old. Basalt breaks down into dark, heavy, fertile clay. It is the reason the farmland north of Lisbon is so much richer than the sandy ground south of the river. |
| Old schist and greywacke | Trás-os-Montes, the Douro valley, most of the Alentejo, the hills of the western Algarve | The oldest rock on the map. It splits into flat slabs, which is why old walls and roofs in these regions are made of stone sheets. This is the ground the Douro and Alentejo vines grow in. |
| Quartzite and slate ridges | Valongo, Serra do Buçaco, Portalegre, Marvão | Narrow, very hard ridges that stand above everything around them. Good views and steep plots. Digging foundations or a pool here costs more than on soft ground. The same rock was quarried for roof slate. |
| Coal-bearing rock | A thin band from Valongo to São Pedro da Cova and Pejão, east of Porto | Portugal's coal came from this narrow strip. The mines are closed. The band is small, but it explains why an industrial mining history sits right next to Porto. |
| Jurassic limestone | Serra de Aire e Candeeiros, Maciço de Sicó, Serra da Arrábida, the Algarve barrocal | Rain slowly dissolves this rock. Water sinks in and travels underground instead of running in rivers, which is why these hills look dry on top and hold huge amounts of water below. The Maciço Calcário Estremenho is one of the largest groundwater stores in the country, with more than 1500 known caves and strong springs such as Olhos de Água and Alviela. It is also the source of Lioz, the stone used across Lisbon buildings and pavements. |
| Cretaceous limestone, sandstone and clay | The Oeste, from Leiria down to Lisbon, and around Torres Vedras | Mixed layers with a lot of clay. Clay swells when it is wet and shrinks when it is dry, so ground movement between seasons is normal here. A soil study before building is worth the money. |
| Miocene and Pliocene sands and clays | Lezíria do Tejo, the Setúbal peninsula, Comporta, Grândola, the Algarve coastal strip | Young and soft. These are the sandy soils under the pine and cork landscape of Comporta and Grândola. Easy to dig, but the ground carries less weight than rock. |
| Recent sand, dunes and river mud | Ria de Aveiro, Ria Formosa, the Tagus flood plain, every beach and river mouth | The youngest and softest ground in the country, and the lowest. Most land in the national flood maps sits on it. Soft ground also shakes more in an earthquake than rock does, which is why building rules class ground from rock to soft sediment and ask for a stronger design on the soft classes. |
The map is shown with modern relief shading, so the same rock looks lighter on a sunlit slope and darker in a valley. The squares above use the true colour taken from the map's own legend panel.
Note on names. Delgado and Choffat used the words of their time. Arcaico is now called Precambrian, and Gotlandiano is now called Silurian. The map also marks things most geological maps leave out, including caves with animal bones, prehistoric settlement sites, mineral springs and working quarries. Delgado dug in those caves himself.
Sources
- Carta Geológica de Portugal, 1:500 000, J. F. N. Delgado and P. Choffat, Direcção dos Trabalhos Geológicos, Paris, 1899. Digitised copy: Gallica, Bibliothèque nationale de France.
- Radon susceptibility: Agência Portuguesa do Ambiente, Mapa de suscetibilidade ao radão.
- Radon plan and the link to granite and syenite ground: Plano Nacional para o Radão, Resolução do Conselho de Ministros 150-A/2022.
- Radon reference level of 300 Bq/m³: Decreto-Lei 108/2018, article 145.
- Flood maps: Decreto-Lei 115/2010, transposing Directive 2007/60/EC.
- Ground classes and earthquake design: NP EN 1998-1 (Eurocode 8) and its Portuguese National Annex.
