In the Local Natural Monument of Canto Marinho we can observe some detailed geoforms, generated in the first stages of the closing of the primitive ocean, the Rheic, which started about 400 million years ago. The crenulations and folds, also in sheaths, which give sinuous waves to the whitish yellow rocks that make up a large part of the local substrate (quartzite) were generated in the margin lands, right in the first collision phase of primitive continents, by the shortening of space, heating and dragging (Carvalhido, 2018).

References:

Carvalhido, Ricardo (2018). Livro de Pedra, Monumentos Naturais Locais de Viana do Castelo – Catálogo. Câmara Municipal de Viana do Castelo, 2ª edição.