The Legal Amazon is not a predominantly plain area. The plain Amazon corresponds to only 7% of the about 5 million square kilometers which form the area, whereas 73.78% of the territory is formed by clearly irregular relief. Inside this area, 16.26% (or 12% of the total in the region) present uneven relief, which is therefore more susceptible to erosion, mainly as a consequence of deforestation.

Information of this kind can be produced based on the Database of Environmental Information, relative to the Legal Amazon, released today by IBGE ( Brazilian Institute of Geography and Statistics). The database makes available on the Internet, free of charge data about the geographic relief found in the area, which are compatible with the scale 1:250,000 (in which 1 cm on the map is equivalent to 2.5 km of land), with analyses by region and state.

Data about relief are presented together with those about vegetation, made available by IBGE in 2008, soil and geology, which must be added to the database in 2010. All of them are generated by systematic mapping activities performed by the institute, besides satellite images, updated bibliographic references and studies conducted by other institutions, and must be constantly updated.  The structure of the database allows its manipulation for the creation of new products derived from the crossing of information, so that they can contribute to studies aimed, among others, at the territory ordering of the Legal Amazon, and be applied as subsidies for public policies of the region. 

The Database of Environmental Information is on the IBGE web site, www.ibge.gov.br, in the “Geosciences”, “Download” section. Files are in the shape file format (vectors), which allows the user to use them, but which can only be read with specific softwares.

The database shows that the predominant types of relief in the Legal Amazon are clearly irregular shapes such as knolls, hills, crests and coastal plains*, which take up 73.78% of the about five million square kilometers which constitute that area.

Plain areas represent 13% of the territory; areas of limestone, 0.08% of the total area, whereas plains subject to temporary floods are found in 13.14% of the area, in which almost half (7% of the total) is the Amazon Plain (formed by the rivers Solimões, Amazonas and affluent rivers.

Considering the territory characterized by irregular relief, 16.26% (or 12% of the total in the area, which is equivalent to 600 thousand km²), are unevenly covered – with very steep areas which are more susceptible to erosion and, consequently, more vulnerable to deforestation (so much so that 3.7% of them have undergone some type of human intervention. The destruction of vegetal coverage of soils worsens the effect of erosion, thus contributing to the worsening of common floods in the Amazon area and causing damage to the population. About 20 million persons live in the 775 municipalities which form the Legal Amazon, according to the 2000 Population Census.  

The Database of Environmental Information presents information collected by IBGE in 566 spots of field sampling, about 16 types of relief (such as knolls, hills, etc), grouped as 162 relief units (shaped with similar altitude, appearance and origin, for example, mountain ranges, plateaus, plains, depressions, tableland and coastal plains), grouped into 4 morphostructural domains (big relief groups formed by the same type of rock). 

·         Glossary:

Legal Amazon: Having been established in article 2 of Law no. 5173, of October 1966, it encompasses the states of Acre, Amapá, Amazonas, Mato Grosso, Pará, Rondônia, Roraima, Tocantins, part of  Maranhão and five municipalities of Goiás. It represents 59% of the Brazilian territory, being present in 775 municipalities inhabited by a little more than 20 million people according to the 2000 Census.

Erosion: It is the wearing away of the soil, by the action of rain, wind, or a glacier.

Erosion destroys the structures which form the soil. They are carried to the lower part of geographic relief and, in general, forming silt in watercourses 

Coastal plain: A surface 20 - 50 meters high, usually with a plain top and adjacent to coastal area.