This singular geological occurrence consists in round blocks resulting from the phenomena of weathering and erosion of the quartzite massif of Arouca. It is possible to observe the phenomenon of onion peel disjunction, where the most external surface is very sandy in contrast to the unaltered quartzdiorite in the block core. Throughout time, the block becomes smaller and rounded with the progressive release of the most external scales. The blocks found at higher altitudes are product of the advanced orthogonal fracturing of the quartzite massif. The blocks more resistant to the physico-chemical changing of the massif are the ones that persist in the landscape, under the shape of block chaos after the lowering of the surrounding land, previously sanded and removed.
Location: Arouca
Location: Arouca
