Boroas Stones from Junqueiro

Geossítio 11 Boroas Stones from Junqueiro

They say it resembles the crust of bread

In the interior of the Serra da Freita plateau, in Junqueiro, the “Pedras Boroas” stand out in the landscape. The rounded blocks of rock identify the rock that exists here: Serra da Freita granite, which takes on peculiar shapes at this geosite. In addition to the rounded blocks, a curious phenomenon called “polygonal fissures” forms a lattice on the surface of these granite blocks, making these “stones” similar to the surface of the crust of traditional cornbread, so popular in the gastronomy of this UNESCO World Geopark. Next to some water lines that drain the area surrounding this geosite, there are small peat bogs, resulting from the accumulation of plant matter, particularly mosses of the Sphagnum genus, which decompose very slowly. Here, we can also see undergrowth made up of heather, gorse, carqueja, insectivorous plants such as the dewdrop, various species of dragonflies and damselflies flitting about, the Iberian frog, the orange-bellied newt and the yellow-spotted salamander.

You can find out more about the region along the paths of the PR15 geotourism trail. This geosite is the venue for the “Filhos da Freita Marathon” trail race.

Este geossítio faz parte do itinerário A: Freita, The Enchanted Mountain.
Saiba mais sobre a Rota dos Geossítios .

Informação Geológica

The Junqueiro boulders are part of one of the residual granite reliefs of the Serra da Freita plateau. Two granite blocks (one of which is displaced from its original position) with very expressive polygonal cracks are particularly noteworthy at this geosite. The polygonal cracks are well individualized and extend across the entire vertical surface of these blocks. They generally have 5 to 6 non-regular sides and are only a few centimeters deep.

According to geomorphologists, the genesis and evolution of these geoforms involves the association of sub-surface and sub-aerial processes. This type of modeling began sub-surface and is directly related to the structure of the rock, as can be seen in the well-defined fissures developed in the vertical fractures of this residual relief, reinforcing the importance of this geosite. This network of fractures/fissures allows for the circulation of water, which encourages physical and chemical processes, and the progression of weathering and erosion, which continues with the sub-aerial exposure of the blocks.