Coastal currents influence the conditions of the coast, in direct relation to the great equatorial ocean current, which is of fundamental importance for navigation. As is known, the great equatorial current splits into two branches near the Brazilian coast. The main one heads north, towards the coast of Guiana, running at no great distance from the coast: its speed varies, near the beach, between three quarters of a mile and a mile and a half, while it is two and a half miles between 40-50 kilometers from the coast. The secondary branch heads towards the south near Capo S. Rocco, taking the name of the Brazilian current: this remains at a greater distance from the coast, reaching, at 250-400 kilometers from it, a speed not exceeding three quarters of a mile. L’ wave of undertow is sometimes dangerous for navigation, as happens during the winter also for the port of São Salvador. Tidal currents sometimes have particular importance. More than 3 km. from the Ilha das Oncas (Island of the Panthers), in the Pará estuary, the tidal wave, called “pororoca”, which goes up the river, reaches a height of more than three meters during sigizial periods. The highest tides in Brazil (maximum observed: 8, 16 m) were recorded along the coast of Maranhão, near the bay of S. Marcos. In the Cearense coast the tide height reaches the average value of m. 2.80 (fluctuating between 1.50 m in the squares and 3.50 m in the sigizies).
According to sportsqna.com, the slope of the seabed is sometimes very uniform, as along the coast of the Alagôas where, in the sigizial periods, coral reefs barely emerge on the shallow waters. Real reefs and reefs sometimes constitute a serious danger to navigation; two parallel reefs are, for example, near the port of Natal. More at noon, near the Capo Branco is a narrow coral reef, at about 1100 m. from the peninsula on which Parahyba stands: the 9-meter isobath runs at a distance of 1200-2800 m. from the cliff.
The variety of soil conditions, which exert an immediate and mediated influence on the intensity and modalities of human settlements and on the prevalence of certain occupations, makes it very difficult to divide the Brazilian area into real geographical regions or complex natural regions.. A subdivision proposed by CM Delgado de Carvalho distinguishes the following four geographical regions, or large natural regions of Brazil: Brazil Amazonico, NE. subequatorial, Vertente oriental dos planaltos, Brazil platinum. Each of these is divided into minor natural regions; so Brazil Amazonico, the largest and least populated region and which roughly corresponds to the Brazilian section of the Amazon basin, includes: the “serrana” or boreal region, made up of the archaic plateaus of the Guianas from which they descend, with a series of waterfalls, impetuous tributaries; the Amazonian depression, a large central plain of low lands covered with dense forests which corresponds to the network of natural river routes, where the population is concentrated; the “chapadão septentrional do planalto brasileiro” (region of the northern plains in the map) and the acrense area.
The subequatorial north – east, extending from the lower Pará valley to that of San Francisco and washed by the Atlantic, corresponds to the area of ancient colonization, is still fairly populated, and includes four natural regions: the Maranhense gulf; the area of Parnahyba, a hilly plateau surrounded by plains; the chains and terraces of the north-eastern side, dominating the semi-arid regions of Brazil, and finally the coast, with the ancient forest, in the uncultivated area of Pernambuco.
The eastern side of the highlands, between the terraces of the Bahian interior relief, the great groove of San Francisco and the ocean, includes five natural regions: the coastal region, protected from the winds, populated in its northern part, swampy and uninhabited in the southern part, on which the states of Bahia and Espirito Santo; the high plains region, generally covered with forests, rich in minerals and precious stones; the San Francisco valley, to which the main reliefs of the central system converge, and which corresponds to the central part of Minas Geraes; the southern mining area, where the climatic conditions favor the densification and prosperity of the population, and finally the basin of the Parahyba do Sul, the Fluminense or Rio de Janeiro region, with its reliefs of archaic and eruptive rocks,
The Brazil platense, between the Paraguay valley and the Atlantic, is a colonization area par excellence, generally high, with excellent climatological and agricultural conditions: it extends in the states of S. Paolo, Santa Catharina, Paraná, in the southern part of the Matto Grosso and Goyaz and in the so-called mineiro triangle. It includes five natural regions: the coastal, of typical tropical production, restricted between the Atlantic, the Serra do Mar and the Serra Geral; the serrana, consisting of the two aforementioned greenhouses, characterized by rich rainfall and low population; that of the plateau (crossed by the tributaries of the Paraná) where crops and forests alternate, where the red soil offers the best soil for coffee, where poultry farming, cattle breeding and the most advanced modern industrial methods allow excellent economic results; the so-called riograndense campanha, a typical farming region; finally the inner plateau in the southern section of the Matto Grosso and Goyaz, where colonization is advancing rapidly.