The Map of Soils (Pedology) presents the main types of soils seen in Maranhão. Located from North to South of the state, ultisols and latosols are the most commonly explored in economical terms, both in agriculture (especially soybean crops), and livestock. Despite their naturally-low level of fertility, these soils have a considerable potential for agricultural use because of their good level of moisture and reduced susceptibility to erosion.

Two types of soils seen in Maranhão must be protected. Entisols, mainly in the southern part of the state, face serious erosion, due to the reduced depth and the occurrence in rugged reliefs. Quartzipsamments, present in the North and South of the state, are mainly formed by quartz, and therefore, they are very susceptible to erosion and retain little water.

The Map of the Terrain of Maranhão portrays one of the most famous landscapes in the state, one of major interest for the tourism industry - Lençóis Maranhenses. It is located northeast in the state, and includes dunes and sandbanks, interspersed with temporary ponds.

The units located in more recently-established land, related to sedimentary quaternary deposits, are identified by a variety of forms of low topography. The forms associated to the drainage networks encompass plains and river terraces, which feature along rivers such as Itapecuru, Mearim, Pindaré, Turiaçu, Parnaíba, Tocantins, Gurupi, among others. On the coast, the highlights are, to the northwest, long peninsulas and islands surrounded by mudflats covered with mangroves, besides areas of dunes, sandbanks and mangroves, to the northeast.

The units located in sedimentary basins encompass chapadas, tabuleiros and depressions elaborated on sedimentary rocks which belong to the Basin - Província Sedimentar do Parnaíba, and are older than the previously mentioned ones. They include the long chapada areas of the center and south of the state, crossed by the draining of Itapecuru and Mearim Rivers, and other residual areas of the Rio da Farinha valley. 

IBGE releases today (Dec 16, 2011) the Vegetation, Geology, Geomorphology and Soil Maps of Maranhão, as part of the thematic maps series on natural resources produced for all the Legal Amazon states.  Using the official scale to represent this state, 1:1400.00 (with each centimeter on paper being equivalent to 14 km of land), the maps were elaborated according to data from IBGE’s Environmental Statistics Database (BDIA), and  updated using bibliographical research, information obtained from field work and from satellite images up to 2010. The maps portray the strong anthropic pressure on the cerrado of Maranhão, which has almost 25% of its area used for agricultural activities, mainly soybean crops.  They also show the underground water potential of this state, which has aquifers with total water storage capacity of 17,500 km³.

The maps, which can be seen at ftp://geoftp.ibge.gov.br/mapas/tematicos/tematico_estadual/, are part of IBGE’s commitment to produce information about natural resources of the whole country until 2014. The release of Thematic Maps of Maranhão and of Land Use Maps of Pará and Sergipe will take place at 9 o’clock today, at IBGE’s State Branch in Pará (331/337, Serzedelo Corrêa Av, ground floor - Nazaré - Belém).

The Vegetation Map shows the pressure exerted by the new Brazilian agricultural frontier on the cerrado of central and southern areas of Maranhão. Agricultural activities in those areas (planted pastures, crops) replaced, at surprising and worrying speed, almost 25% of the cerrado, and the area covered by natural vegetation was reduced from 74,288,57km² to the current 57,130,04 km².

After years of logging practices, forests have been restricted to protection areas only, especially Indian reservations. The map shows that the remaining area of Floresta Densa (Dense Forest), for example, has now only 31% of its original size, amounting to 19,707.61km². Considering the Semi-deciduous and Deciduous Forests, only 45% and 25% of native areas have been left; Floresta Aberta (Open Forest) was represented on the map in the northwestern part of the state with only 27.5 km², what corresponds to 0.09% of its original area.

Produced with the aid of satellite images and the update of surveys of the RADAMBRASIÇ Project (which was in effect between 1970 and 1985 to provide radar aerial images of several areas of the Brazilian territory, especially the Amazon), the vegetation map represents three continental Brazilian biomes: Amazon, Cerrado and Caatinga, with six main types of vegetation: Dense Ombrophilous Forest (with tree that do not lose their leaves in the dry season), Open Ombrophilous Forest (full of babacu palm and/or vines), Seasonal Semi-deciduous Forest (with tree that lose part of their leaves in the dry season), Seasonal Deciduous Forest (with trees that lose more than 50% of the leaves in the dry season), Savannah (Cerrado) and Steppe-Savannah (Caatinga of Arid Desert Areas) and Areas of Pioneer Formations (meadows and mangroves, mainly).  

The Geological Map shows the underground water potential of Maranhão, pointing to the presence of aquifiers that can be used for human consumption with  good-quality and low-cost water. Located in an area called Província Estrutural Parnaíba (which covers more than 90% of the state), on the formations of Cabeças, Serra Grande, Sambaíba, Corda, Grajáu, Itapecuru, Ipixuna and Barreiras, the aquifiers amounted to a total volume of 17,500 km³, volumetric flow rates that can reach 1,000 m³/h.

On the map, it is also possible to see AM area of major importance for tourism: Província Estrutural Costeira, which occupies most of the coast of Maranhão as dunes (marine, river and marine, Aeolian, from pleistocene to holocene deposits), which, together, form Lençóis Maranhenses and Baixada Maranhense.

The map also shows the use of the areas used agricultural activities (Penitentes, Alpercatas and Espigão Mestre Mountain Ranges) which work as a place for storage and suppliers of the water that flow in water basins of the region, all over the South, to the West and southwest of the state. That causes concern about the environmental impacts. Agricultural activity damages the process of infiltration and brings contamination due to the use of agricultural pesticides.

In Província Estrutural Gurupi, located in the northwestern area, the highlight is gold, which has been traditionally extracted from mines. The carbonated deposits of Cretaceous Age seen in the formation Codó have significant amounts of limestone, used partially for the production of cement in factories installed in the city of Codó and also as a way to correct the acidity of soils of the region and neighboring areas, such as Pará and Piauí.  

Monumental sets of geological fault, under the form of alignments of mountain ranges and draining networks cross the territory of Maranhão. The main highlights are Pirapemas (NE-SO), Picos-Santa Inês (NO-SE), Tianguá-Carolina (ENE-OSO) and Transbrasiliano (NE-SO), and point to areas which are economically-relevant, some favorable to the concentration of hydrocarbons. As an example, one can mention the natural gas reserve, discovered in 2010, in the municipality of Capinzal do Norte (Bacia do Grajaú), in an area of influence of the group of faults called Picos-Santa Inês. In a region of the municipality called Balsas, in areas affected by the group of faults of Tinguá-Carolina, in a well drilled by Petrobrás in the 1960’s, there were traces of natural gas.