On this route and its surroundings there are outcrops of granitic rocks, formed after the deformation phase of the Hercynian orogeny (occurring between the Devonian and Permian periods, characterized by huge stresses that gave origin to large fractures that allowed the rise and intrusion of magma in the earth’s crust). These are the Gerês’ granite (biotitic granite, with porphyritic texture and medium/coarse grain) and the Tieiras’ granite (fine grain biotitic granite, with a porphyritic tendency). The latter only occupies a small area of the route, exactly in the place from where it got his name (Tieiras).
Walking along the valley of Lamas de Mouro, one can see several large granite blocks, deposited in an isolated way at the bottom of the valley. These may be the result of an eventual land slip that occurred in the granite outcrop that can be seen on top of the slope.
If you are walking the route after a night with below zero temperatures and no rain, please pay attention to the soil. Amongst other interesting aspects you will be able to see needle-like crystals of ice (also known as Pipkrakes), that develop together and in large numbers, perpendicular to the soil or slightly curved. This phenomenon is the result of the existence of water and below-zero temperatures on the soil. These Pipkrakes can prise off the dead matter above them, soil particles and stones, up to several centimetres away from the soil.