(Plural Intentional) Along the Amazon there are places where rivers join but because of differences in qualities of the water they do not mix for miles. The most famous in at Manaus where the Rio Negro meet the Amazon. The Amazon, in Brazil it is known as the Solimões until it joins the Negro, is a pale, sandy river carrying sediment down from the Andes. The Rio Negro is a “blak water” river which flows over the hard Guyana Shield so picks up little in the way of sediment. It is colored by decaying vegetable matter so its water is black, more readily reflecting the colors of the sky.

The rivers join and flow side by side without mixing for 6 km (3.7 miles) without mixing, they flow another 60 km (37 miles) before mixing completely. You can see this from a satellite photo from Google Maps.

The reason they don’t mix quickly is not only because of the density created by the things they are carrying but because they flow at different speeds. The Negro flows at 2 kph while the Amazon flows two to three times more quickly. The Rio Negro is 280 Celsius (820 F) while the Amazon is around 220 Celsius (720F). These pictures from Volendam show the difference.

There is a similar meeting at Santerém where the clear water Tapajós River which flows over the Brazilian shield meets the Amazon. The rivers flow together without mixing for only about 10 km (6 miles) but to me the delineation seemed sharper than upriver in Manaus.

In Santerém we experienced the meeting from both the deck of Volendam and from Gil Serique’s smaller boat.