Les systèmes fluviaux et les plaines inondables du Brésil, du Pérou, de l'Équateur, de la Colombie et du Venezuela, dont les eaux se déversent dans la Solimões et ses affluents, sont appelés "la haute Amazonie
I belive it it O because <span>An O horizon has at least 20% </span>organic matter<span> by mass. Two main scenarios result in the formation of an O horizon: saturated, </span>anaerobic<span> conditions (wetlands) or high production of leaf litter in forested areas. Anaerobic conditions slow the </span>decomposition<span> process and allow organic material to accumulate. An O horizon can have various stages of decomposed organic matter: highly decomposed, sapric; moderately decomposed, hemic; and minimally decomposed, fibric. In a fibric O layer, plant matter is recognizable (e.g., it is possible to identify a leaf). Sapric material is broken down into much finer matter and is unrecognizable as a plant part. Hemic is in between sapric and fibric, with some barely recognizable plant material present. It is possible to have multiple O horizons stacked upon one another exhibiting different decomposition stages. Because of their organic content, these horizons are typically black or dark brown in color. The dominant processes of the O horizon are </span>additions<span> of organic matter, and </span><span>transformations </span><span>from fibric to sapric
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<span>An island can become a seamount only if there is native and active volcanic activity that is able to raise the landmass sufficiently above sealevel.</span>
