linguistic:voice_change, structural:scholar_edition
Meeting of Waters

The Meeting of Waters (Portuguese: Encontro das Àguas) is a natural phenomenon caused by the confluence of the Rio Negro's dark water and the Solimões River's muddy brown water that come together to form the Amazonas River. For 6 km (3.7 mi) or more, both rivers' waters run side by side without mixing. The reason for this is not clear, although it is likely that the main factors are differences in the speed of the current, the volumes of water and the different densities of the two rivers. It is not thought that other differences between the two rivers (temperature and acidity) affect the mixing process significantly. The Negro River flows approximately 2 km/h (1.2 mph) at 28 °C (82 °F), while the Solimões River flows 4 to 6 km/h (2.5 to 3.7 mph) at 22 °C (72 °F).