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Amazon Lowlands an 
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| Highlands s| 
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ELEVATION 
] Under 600 feet 
Over 600 feet 
ik od 
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Figure 2.—Distribution of lowlands and highlands in Brazil. 
vessels of less than 14-foot draft can navigate the 
river as far as Iquitos in eastern Peru. The Amazon 
tributaries can be traveled by river boats to the falls 
and rapids which occur where the streams drop from 
the low uplands to the alluvial plain. The Amazon 
River provides the most important means of access 
More than half the 
area of Brazil, the Amazon lowlands and part of the 
to a large part of the forests. 
Brazilian Highlands. lies in the Amazon Basin. 
The Amazon lowlands. most densely forested area 
of the country, can be divided into four general 
categories in relation to the river waters: Perma- 
nently swampy (igap6), seasonally flooded (varzea). 
dry alluvial plain, and low uplands rising to 600 feet 
in elevation (fig. 3). 
soils while the last has residual soils derived from 
The first three have alluvial 
the volcanic and metamorphic rock formations. 
The alluvial plain of the Amazon extends some 
800 miles from south to north at the foot of the 
Low uplands 
(fa River rapids 
Ory 
Andes. west of the Brazilian border. 
It narrows like 
a funnel, becoming less than 50 miles wide at its 
narrowest point, and again broadens on either side 
of the river’s mouth. Of this total plain, the por- 
tion that floods annually is seldom more than 50 
miles wide yet is estimated to aggregate 150,000 
square miles. A large part of this lies between the 
median water level and the high water level or flood 
stage of the rivers; this area is called “‘varzea.” 
The varzea drys quickly and its forests can be readily 
logged after the high water recedes. Fertile soils | 
created by silt and sand deposits from annual floods | 
have encouraged permanent settlement close to | 
varzea lands. Accordingly, labor is more plentiful | 
close to the streams, and these forests are the prin- | 
cipal source of timber in the Amazon lowlands. | 
The poorly drained areas where flood waters stand § 
These poorly | 
drained areas support a dense growth of trees, chiefly | 
These areas, old streambeds and | 
other low flats chiefly near the confluence of streams, 
for long periods are called igapos. 
noncommercial. 
are scattered throughout the varzea and sometimes | 
seriously impede the logging of timberlands of the | 
varzea that lie behind them. | 
The dry alluvial plain lies between the various | 
streams and above high water level. These dry | 
lands. representing earlier flood plains, account for | 
the largest area and contain the best part of the | 
Amazon forests. | 
The alluvial soils of the Amazon lowlands are | 
characteristically gray in color. They vary trom | 
silty sands occurring in relatively narrow belts of | 
slightly higher land adjacent to present and former 
streambeds to clays in flat areas where water stands | 
for long periods of time. 
The low uplands rising above the alluvial plain to } 
an elevation of about 600 feet occupy a considerable | 
portion of the Amazon Basin. The red and yellow 
soils of this area are derived from the crystalline | 
igneous rocks. In general they are friable and easy | 
to tll. They have light-colored surface layers and _ 
High water 
— Low woter 
Residual volcanic rock 
Alluvial deposits 
Main river 
Figure 3.—Classification of Amazon lowlands in relation to stages of the river level. 
2, FOREST RESOURCE REPORT 16, U.S. DEPARTMENT OF AGRICULTURE 
