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TROPICAL RAINFORESTS:
The Understory
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About this site
Providing tropical forest news, statistics, photos, and information, rainforests.mongabay.com is the world's most popular rainforest site. [more] |
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Where Are the Rocks?
The Amazon basin is formed by the depression of pre-Cambrian bedrock, and is surrounded on three sides by the Andes
to the West, and the Brazilian and Guyana shields to the South and North, respectively. The earth of this basin
is made up of sedimentary layers of soft clay and sand deposits over 13,000 feet (4,000 m) thick. Therefore, in
the Central Amazon basin virtually no rocks are found since they either would have to stay intact on the long journey
from the Andes or lie on the river bottom. Since rocks are useful for sharpening machetes along with other tasks,
rocks are valuable in the rainforest. In some areas, a person's wealth is determined by the number of rocks the
family owns. Barges still carry rocks to parts of the Amazon to sell and trade with native peoples.
Another result from the instability of the clay soils of the Amazon Basin and other tropical regions, is difficulty
in constructing roads. Some blame the failure of the Trans-Amazonian highway—sections of which sank into the
ground—on the characteristics of these soils.
Characterization of the Amazon Basin in terms of the soil's physical qualities and formations
Continued: Rainforest floor
Unless otherwise specified, this article was written by Rhett A. Butler [Bibliographic citation for this page]
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Recent news
Amazon deforestation rate falls to lowest on record
(8/10/2007) Deforestation rates in the Brazilian Amazon for the previous year were the lowest on record, according to preliminary figures released by INPE, Brazil's National Institute of Space Research.
Lowland rainforest less diverse than previously thought
(8/9/2007) While rainforests are the world's libraries of biodiversity, species richness may be more evenly distributed in some forests than in others, reports an extensive new study by an international team of entomologists and botanists. The work, published in the current issue of the journal Nature, has important implications for forest management and conservation strategies.
Experts: parks effectively protect rainforest in Peru
(8/9/2007) High-resolution satellite monitoring of the Amazon rainforest in Peru shows that land-use and conservation policies have had a measurable impact on deforestation rates. The research is published in the August 9, 2007, on-line edition of Science Express.
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