Baixo (islet)

This islet, also known as the Ilhéu da Cal (‘lime islet’), lies next to the island of Porto Santo (‘holy harbour’), from which it is separated by a channel, the Boqueirão de Baixo (‘lower gap’). It stands at the southern tip of the island, at the western end of the wide bay, opposite the locality of Calheta (‘small cove’). For centuries all the limestone that supplies the raw material for the lime used in Madeiran building has been quarried on this islet, and it still is. The quarrying follows the seam, forming long galleries with tall columns or pillars to prevent collapses. It is carried out at several points, and each group of workers employed at the various quarrying sites is called a band (rancho). The stone is taxed on export to Madeira, the duty being collected at the Funchal customs house, and it is one of the most valuable sources of revenue of the Municipal Council (Câmara Municipal) of Porto Santo. The islet is fairly large, and rabbits are still plentiful there, despite the constant poaching of these rodents.

The islet’s ground has been uplifted, as shown by the limestone lying far above sea level and by the sea shells, corals and beach-like stones found in the formation. The fossils date from the Upper Miocene. About fifty species have been found, both in the limestone and in the adjacent tuffs, among them bryozoans, corals, sea urchins, lamellibranch molluscs and gastropods; they were described by Carlos Mayer in Hartung’s work on the geology of the archipelago. The limestone formation is covered by subaerial lavas.

On the islet’s coasts there are some caves with salt stalactites, and at Portinho (‘little harbour’) there are large excavations cut by man in the tuffs, together with a cistern whose water is strongly salty because the rock is permeable.