MADEIRA RIVER

Portuguese Rio Madeira, major tributary of the Amazon. It is formed by the junction of the Mamor and Beni rivers at Villa Bella, Bolivia, and flows northward forming the border between Bolivia and Brazil for approximately 60 miles (100 km). After receiving the Rio Abun, the Madeira meanders northeastward in Brazil through Rondnia and Amazonas states to its junction with the Amazon River, 90 miles (145 km) east of Manaus. A distributary of the Madeira flows into the Amazon about 100 miles (160 km) farther downstream, creating the marshy island of Tupinambarama. The Madeira is 2,082 miles (3,352 km) long from the upper reaches of the Mamor, and its general width is about 1/2 mile. It is navigable by seagoing vessels most of the year from its mouth on the Amazon to the Cachoeira (falls) de Santo Antnio 807 miles (1,300 km) upstream, the first of 19 falls or rapids that block further passage, near the town of Prto Velho, Braz. The Estrada de Ferro (railway) Madeira-Mamor, extending for 227 miles (365 km) between Prto Velho and Guajar-Mirim, provides a link with the upper course of the Madeira River. Although exploration of the Madeira Valley began in the 16th century, parts of the region were first mapped via satellite in the late 1970s. The tropical rain forest through which the river flows is almost uninhabited except for occasional settlements of Indians and mestizos who dwell along the riverbanks and gather such forest products as Brazil nuts and rubber.