About this place

Manaus is the capital city of the state of Amazonas in northern Brazil. It is situated in the heart of the Amazon rainforest, at the confluence of the Negro and Solimões rivers. With a population of over 2.2 million, it is the most populous city in the Amazon region and a major inland port.

The city was founded by the Portuguese in 1669 as a small fort. For centuries, it remained a remote and isolated settlement. This changed dramatically in the late 19th and early 20th centuries with the onset of the Amazon Rubber Boom. Manaus became the center of the world's rubber trade, attracting immense wealth and transforming into a cosmopolitan metropolis. During this era, wealthy rubber barons funded the construction of lavish buildings, the most famous of which is the Teatro Amazonas, an opulent opera house opened in 1896. The boom ended abruptly in the 1910s when rubber plantations in Southeast Asia broke the Amazon's monopoly, causing the city's economy to decline. Today, Manaus has re-emerged as a major industrial center, largely due to the creation of a Free Economic Zone.

The Meeting of Waters (Encontro das Águas)

The most prominent natural phenomenon near Manaus is the Meeting of Waters, the point where two major Amazonian tributaries, the Rio Negro and the Rio Solimões, converge. The defining characteristic of this confluence is that the waters of the two rivers flow side-by-side in the same channel for approximately 6 to 10 kilometers without mixing, creating a sharp, visible boundary line.

The two rivers have distinctly different characteristics, which is the reason for this phenomenon. The Rio Negro is a "blackwater" river. Its water is dark, almost the color of black tea, due to the high concentration of dissolved organic acids (humic and fulvic acids) from the decomposition of vegetation in the swamps and forests it drains. It is very low in sediment, slow-moving (about 2-3 km/h), warmer (around 28°C), and highly acidic.

In contrast, the Rio Solimões is a "whitewater" river, though its color is a dense, muddy, café-au-lait brown. This is because it carries a heavy load of suspended sediments, sand, and silt eroded from the Andes Mountains, where it originates. It is significantly faster-flowing (about 6-8 km/h), cooler (around 22°C), and has a more neutral pH. The differences in temperature, density (due to sediment), speed, and chemical composition are so pronounced that they create a barrier, preventing the two bodies of water from readily mixing. Eventually, the turbulence of the combined flow downstream forces the waters to merge, at which point the river is officially known as the Amazon River.