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They are steep walls found on the coast of almost all the world, designed by the action of the sea in the last 180 million years. They appear by the action of maritime erosion in the intervals between ice ages, when the level of the oceans can rise up to 12 meters. On these occasions, the water advances over the continents and erodes the land closest to the coast. “When the sea meets lowlands, the action of the water on land generally forms the beaches of the coast. When it hits higher areas, the plateau, erosion is concentrated in the lower part of the terrain, producing the cliffs”, says geologist George Satander Sá Freire, from the Federal University of Ceará (UFC). In Brazil, cliffs appear at various points along the coast, reaching more than 20 meters in height. The appearance of the walls varies according to the type of rock that the sea carved. From Amapá to Rio de Janeiro, reddish cliffs predominate, formed from sandstone terrain.
In the south of the country, dark cliffs, carved in granite, are more common. In addition to the slopes close to the sea, geologists are also studying walls up to 2 kilometers from the coast, the so-called dead cliffs. They provide clues about ocean activity and show how far the sea has advanced. Despite the incredible look for tourism and the importance for science, Brazilian environmentalists have already triggered the red light for the devastation of these formations, especially in the Northeast. In Alagoas, where the vegetation at the top of the slopes has given way to sugar cane plantations, the soil is eroded by fires and the cliffs end up falling into the sea, suffocating corals close to the coast. “And in Ceará there is even open sewage running from the top of some cliffs onto the beach, aggravating pollution and the threat of landslides on the slopes”, says George.