Its westernmost source is high in the Andes Mountains, within 100 miles (160 km) of the Pacific Ocean, and its mouth is in the Atlantic Ocean, on the northeastern coast of Brazil.
Using the definition of the river’s source as being the farthest point from which water could flow into the ocean and where that water flows year-round (thereby eliminating those rivers that freeze in winter), he concluded that the source was Carruhasanta Creek on Mount Mismi.
By the early 21st century, advanced satellite-imagery technology was allowing researchers to match the river’s dimensions even more precisely.
Amazon River, Portuguese Rio Amazonas, Spanish Río Amazonas, also called Río Marañón and Rio Solimões, the greatest river of South America and the largest drainage system in the world in terms of the volume of its flow and the area of its basin.
The total length of the river—as measured from the headwaters of the Ucayali-Apurímac river system in southern Peru—is at least 4,000 miles (6,400 km), which makes it slightly shorter than the Nile River but still the equivalent of the distance from New York City to Rome.
This immense volume of fresh water dilutes the ocean’s saltiness for more than 100 miles (160 km) from shore..