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Because the chemical composition, temperature and speed of the two are different. Over a course of about 6 km, the Negro and Solimões rivers run side by side without mixing before becoming one – the great Amazon River. According to Karime Bentes, chemistry professor at the Federal University of Amazonas (Ufam), the phenomenon, known as the Meeting of the Waters, happens due to the difference in “composition and acidity, combined with the temperature and speed of the two currents”. The Rio Negro, which carries a large amount of organic matter from its source in Colombia (which gives its water a dark tone), flows at about 2 km/h with a temperature of 28 °C. On the other hand, the Solimões, which rises in the Peruvian Andes and has water with a muddy appearance, due to a load of sediments coming from the erosion of volcanic soils, travels at an approximate speed of 4 to 6 km/h at a temperature of 22 °C.
– How many Amazons are there?
Question Caina Chiarini, Sao Paulo, SP
CONSULTANCY Karime Bentes, professor of chemistry at the Federal University of Amazonas (Ufam), Rodrigo Marques, chemist at the Department of Physical Chemistry at Unesp, and Claudio Furukawa, physicist at the Institute of Physics at the University of São Paulo (USP)