The sertão (, plural sertões) is the "hinterland" or "backcountry". In Brazil, it refers both to one of the four sub-regions of the Northeast Region of Brazil (similar to the specific association of "outback" with Australia in English) or the hinterlands of the country in general. Northeast Brazil is largely covered in a scrubby upland forest called a caatingas. Its borders are not precise. It is an economically poor region that is well-known in Brazilian culture, with a rich history and much folklore, something like the American South. The sertão is also detailed within the famous book of Brazilian literature Os Sertões (The Backlands), which was written by the Brazilian author Euclides da Cunha. Originally the term referred to the vast hinterlands of Asia and South America that Portuguese explorers encountered. In Brazil, it referred to backlands away from the Atlantic coastal regions where the Portuguese first settled in South America in the early sixteenth century. A Brazilian historian once referred to colonial life in Brazil as a "civilization of crabs", as most settlers clung to the shoreline, with few trying to make inroads into the sertão. In modern terms, "sertão" refers to a semi-arid region in northeastern Brazil, comprising parts of the states of Alagoas, Bahia, Pernambuco, Paraíba, Rio Grande do Norte, Ceará, Maranhão, Piauí, Sergipe, and Minas Gerais. Geographically, the sertão consists mainly of low uplands that form part of the Brazilian highlands. Most parts of the sertão are between and above sea level, with higher elevations found on the eastern edge in the Borborema Plateau, where it merges into a sub-humid region known as agreste, in the Serra da Ibiapaba in western Ceará and in the Serro do Periquito of central Pernambuco. In the north, the sertão extends to the northern coastal plains of Rio Grande do Norte state, while to the south it ends gradually in the northern part of Minas Gerais. Two major rivers cross the sertão, the Jaguaribe and further east the Piranhas, and to the south, the larger São Francisco River is in part in the sertão. Smaller rivers dry up at the end of the rainy season. The term sertão is also used in Portuguese to refer to the Brazilian hinterland in general, regardless of region. It is this sense that corresponds to sertão music, música sertaneja, roughly "country music". To avoid ambiguity, the region in the northeast is sometimes called the