The tides do not arrive to cover the band delinquent of the rivers biggest, but they invade igaraps and for them they overflow for the fertile valley low. During the rainy station this stretch is almost constantly flooded and atoladio, but with the advance of the dry station it goes acquiring consistency until becoming firm. The width of the fertile valley low can reach some kilometers, and its area is well bigger of what of the high fertile valley. Dislocating itself more for the interior, it is come across with stretches where the quota is lower in relation to the previous ones, and are flooded for the water of rains, for the most part of the year. This band has very bigger extension from what the cited ones in remote times had previously and only received influence of the tides and the river Amazon. This stretch currently is formed to a large extent, for the deposition of vegetal debris in decomposition in the estagnada and dark water.
They are the subject to flooding fields for water candy (igaps). The ground of this stretch has watery and soft consistency. A factor that concurs for the formation of the ground of the fertile valleys is the organic substance, understanding itself as this the vegetal debris that fall on the ground, unfastened of the florstico covering. In such a way, in high fertile valleys, being the covering, generally, constituted of the bush, the substance organic if it unfastens of the forest ceiling and the sub-forest while in the stretches of quota lower, the organic substance comes from the covering formed for shrub or herbaceous plants. The agricultural possibilities and the conditions of work also are different in the high fertile valley, the fertile valley low and igaps. The high fertile valleys are of more easy manuscript and immediate agricultural possibilities. Since that the proper times for each culture are respected, these lands delinquents could be cultivated without previous draining.