Rivers in the Amazon differ greatly in color according to the type and quantity of silt. Rivers
that arise in the Andes are rich with silt and consequently have a pale brown color, like coffee
with cream. These are called "white water" rivers (nothing to do with river rafting!). The largest
such river is the Amazon main stream itself. Rivers that arise in ancient cratons (rocky massifs)
such as the Guyana shield in northeastern Brazil, have low silt levels and most of the suspended
solids derive from plant matter. This material gives the water a dark appearance, like coffee
without cream. These are the so-called "black water" rivers. The biggest of these is the Rio Negro,
whose name itself means Black River. Where these two kinds of rivers meet, the waters do not blend
right away but remain separate for many miles downstream. The most spectacular of the "meeting of
waters" is where the Rio Negro runs into the Amazon main stream, a phenomenon visible from space.
(See meeting of waters for what this looks like on the river itself.
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