The Amazon River's 6,400-km Journey: From Andean Glacier to Atlantic Giant

The Amazon is the world's largest river by discharge (209,000 m³/s) and longest (6,992 km per recent Brazilian studies). Its journey stitches a continent together.

1. Birth: Apacheta Spring (5,170 m)

On Nevado Mismi (Arequipa, Peru), a glacial trickle emerges. Controversial "true source" – Mantaro drainage may be longer. Either way: Andean snowmelt + orographic rain.

2. Upper: Apurímac → Ene → Tambo → Ucayali

Whitewater canyons (Class V), cloud forest, Asháninka territory. 1,600 km to Atalaya. Sediment load begins.

3. Confluence: Ucayali + Marañón = Amazon (proper)

At Nauta, Peru. Marañón brings Andean sediments; Ucayali brings lowland organics. River widens to 2–5 km.

4. Middle: The Wild Meander Belt (Peru → Brazil)

• Anabranching channels, oxbow lakes (cochas), várzea floodforest.
• Tributaries: Huallaga, Napo, Putumayo, Javari (border).
• Iquitos (400,000) – largest city unreachable by road.

5. Brazilian Lowlands: The Great Tributaries Join

6. The Amazon Fan & Mouth

Near Belém, the river fans into a 300-km-wide estuary (Marajó Bay). Tidal bore (pororoca) surges 4 m upriver. Marajó Island (40,000 km²) splits the discharge. Freshwater plume extends 200 km into Atlantic—visible from space.

Global Significance

• 20% of Earth's river discharge.
• Exports 1.2 Gt sediment/yr – builds continental shelf.
• Drives Atlantic meridional overturning (freshwater lid).
• Holds 10% of known species; 400+ Indigenous groups.

Threats

Dams (300+ planned/built), deforestation (flying rivers), mining mercury, climate dieback. The journey still flows—but for how long?