(i) The northern part of Brazil lying between the Equator and the Tropic of Capricorn, i.e. in the Tropical zone is covered largely by the Amazon Plains.
(ii) Amazon plains lying between the Guyana highlands and the Brazilian highlands form the largest plain land of Brazil.
(iii) The Amazon valley receives very heavy rainfall of around 2000 mm and the average temperature here is 25 to 28°C.
(iv) These conditions favor the dense growth of tropical rain forests. Due to frequent flooding and dense undergrowth, these forests are largely inaccessible.