Amazon River

The Amazon River (UK: /ˈæməzən/, US: /ˈæməzɒn/; Portuguese: rio Amazonas, Spanish: río Amazonas) in South America is the largest river by discharge of water in the world. It is also one of the longest rivers, maybe even the longest, but this is debated with the Nile.

The headwaters of the Apurímac River begin in Nevado Mismi in Peru. These were thought to be the most distant source of the Amazon basin for a long time. However, a study in 2014 found that the headwaters of the Mantaro River on the Cordillera Rumi Cruz in Peru might be the true source. The Mantaro and Apurímac rivers join with other tributaries to form the Ucayali River. This river meets the Marañón River upstream of Iquitos, Peru, forming what many countries consider the main stem of the Amazon. In Brazil, this section is called the Solimões River until it meets the Rio Negro at the Meeting of Waters (Portuguese: Encontro das Águas) near Manaus, the largest city on the river.

The Amazon River has a very large amount of water flowing through it. It releases about 215,000–230,000 cubic meters of water every second. This is more water than the next seven largest rivers combined. The Amazon River and its basin cover a huge area, about 7,000,000 square kilometers, making it the largest drainage basin in the world. By the time the Amazon reaches Brazil, it already has more water than any other river, and it flows into the Atlantic Ocean.

Etymology

The Amazon River was first called the Marañón by Europeans. This name is still used in Peru and in the Brazilian state of Maranhão. Later, it became known as Rio Amazonas in Spanish and Portuguese.

The name Rio Amazonas came from an event where native warriors, led by women, attacked an expedition led by Francisco de Orellana in the 1500s. The women warriors reminded him of the Amazon warriors from ancient Greek mythology. The word "Amazon" may come from an old Iranian word meaning "fighting together" or "warriors."

History

Geological history

Geological studies show that the Amazon River once flowed in the opposite direction—from east to west. The Andes Mountains formed later, blocking its path to the Pacific Ocean. This made the river change direction to flow into the Atlantic Ocean.

Pre-Columbian era

During early times, Amazonian societies helped shape South America's highland farming systems. Trade with Andean civilizations in the headwaters of the Andes supported the growth of higher-altitude cultures like the Muisca and Incas. Early settlements were often on low hills or mounds.

Shell mounds are the oldest signs of people living there. These mounds, made from human waste, date from between 7500 BC and 4000 BC. The areas around the Amazon River were home to large indigenous societies, mainly chiefdoms that built towns and cities. By 1541, when the Spanish conquistador De Orellana traveled the Amazon, more than 3 million indigenous people lived there.

Arrival of Europeans

In March 1500, the Spanish explorer Vicente Yáñez Pinzón was the first European to sail up the Amazon River. He named it Río Santa María del Mar Dulce, later called Mar Dulce, meaning "sweet sea" because its fresh water flows into the ocean. Another Spanish explorer, Francisco de Orellana, was the first European to travel from the river's source in the Andes to its mouth.

Exploration

Gonzalo Pizarro set out in 1541 to explore east of Quito looking for El Dorado, a legendary city of gold, and La Canela, the "valley of cinnamon". He was with his second-in-command, Francisco de Orellana. Their journey reached the mouth of the Amazon on August 24, 1542, proving the river could be navigated.

Scientific exploration

From the 18th century to the mid-19th century, many scientists explored the Amazon River and its basin.

• Charles Marie de La Condamine explored the river in 1743.
• Alexander von Humboldt, 1799–1804
• Johann Baptist von Spix and Carl Friedrich Philipp von Martius, 1817–1820
• Georg von Langsdorff, 1826–1828
• Henry Walter Bates and Alfred Russel Wallace, 1848–1859
• Richard Spruce, 1849–1864

Post-colonial exploitation and settlement

The Cabanagem revolt (1835–1840) was a rebellion against the white ruling class. In 1850, about 300,000 people lived in the Brazilian part of the Amazon basin.

20th-century development

Since colonial times, the Portuguese part of the Amazon basin has stayed mostly wild, with many indigenous people living there.

Four centuries after Europeans found the Amazon River, the area farmed in the basin was tiny—about 65 km² (25 sq mi), not counting small farms near the Andes. This changed a lot in the 20th century.

In 2014, Manaus had 1.9 million people, making it the largest city on the Amazon. It is about half of the population of Amazonas, the largest state in Brazil. Most people in Manaus are pardo (mixed heritage) or white.

The Amazon River has no dams, but about 412 dams are on its tributary rivers. Of these, 151 are on six main tributaries. Only 4% of the Amazon's hydropower potential has been used in countries like Brazil, but many more dams are planned. Scientists worry that building more dams will hurt the Amazon's plants and animals by disrupting fish migration, reducing nutrients, and clearing forests.

Course

Main article: Source of the Amazon River

The Amazon River starts in the Río Mantaro area. For a long time, people thought it began at the Apurímac River near Nevado Mismi. But in 2014, scientists learned that the Mantaro River is actually farther from the sea.

The Amazon River is formed from several smaller rivers. The Apurímac and Mantaro rivers join to create the Ene River. The Ene River then joins others to become the Ucayali River. The Ucayali meets the Marañón River, and this is where most people say the Amazon River starts.

The Amazon River flows through Brazil and Peru, and it forms part of the border between Colombia and Peru. It has many important smaller rivers, such as the Putumayo, Caquetá, Vaupés, Guainía, Morona, Pastaza, Napo, and Huallaga. In some places, the river splits into many channels, making many islands.

The Amazon River ends at the Atlantic Ocean near the city of Belém. The exact place and width of where it meets the ocean are not fully agreed on because of the area's unique landscape. Some measurements say the mouth is over 300 kilometers wide!

There are no bridges that cross the whole width of the Amazon River. This is mainly because the river flows through a rainforest with very few roads and cities. People usually cross by ferry. The Manaus Iranduba Bridge crosses the Rio Negro, a major smaller river of the Amazon, linking the cities of Manaus and Iranduba.

There has been a long discussion about whether the Amazon or the Nile is the world's longest river. Different ways of measuring give different answers, and scientists are still talking about this today. Some say the Amazon is longer, while others say the Nile is longer.

Watershed

Main article: Amazon basin

The Amazon basin is the largest in the world. It covers about 40% of South America. It stretches from Iquitos in Peru across Brazil to the Atlantic Ocean. The basin collects water from places as far north as 5 degrees north latitude to as far south as 20 degrees south latitude.

Each rainy season, the Amazon River and its tributaries flood large forested areas. During the wet season, the flooded area grows to 350,000 km². The Amazon sends a huge amount of water into the Atlantic Ocean—up to 300,000 m³ per second during the rainy season. This fresh water creates a large plume in the ocean, changing its color and making it less salty over a wide area.

Discharge

The Amazon River has the largest amount of water flowing out of any river in the world. Scientists measured the water flow near the river’s mouth and found that about 7,200 cubic kilometers of water flows out each year. This is a lot of water — enough to fill many huge swimming pools!

We can also learn about the river’s water flow at different places along its path. For example, at places called Santarém, Óbidos, and Itacoatiara, scientists have measured how much water the Amazon River carries. Even at these spots farther upstream, the Amazon still moves a huge amount of water. The Amazon’s water flow can also be compared to other big rivers, like the Tocantins River.

Sediment load

The Amazon River carries a lot of sediment. At a place called Óbidos, scientists found that the river moves about 754 × 10⁶ tons of sediment each year. This shows how strong the Amazon River is and how it helps shape the land around it.

Flooding

The Amazon River does not flood all at once. Some parts start flooding in November and keep rising until June. The Rio Negro begins to rise in February or March and starts to fall by June. The Madeira River has its flood season two months earlier than most of the Amazon.

Between Manacapuru and Óbidos, the Amazon River is between 20 and 26 metres deep. Near Manacapuru, the river is only about 24 metres above sea level. Large ocean ships can travel up to Manaus, 1,500 kilometres from the mouth of the river. Smaller ships can go as far as Iquitos, Peru. Even smaller boats can go further, reaching up to the Pongo de Manseriche.

Each year, high tides in the Atlantic send a powerful wave up the Amazon delta. This wave, called the pororoca, can be up to 7.6 metres high and travel far inland.

Geology

The Amazon River began as a river a very long time ago. About 11 million years ago, it looked different from today.

Long ago, when Africa and South America were connected, the area that is now the Amazon flowed westward. About 80 million years ago, the continents split apart. The rise of the Andes mountains changed the river's path, turning the area into a large lake. Over time, this lake became the river we know today, helping create the Amazon rainforest. There is also a hidden aquifer called the Hamza River that runs parallel to the Amazon.

Protected areas

The Amazon River flows through special places that help keep its environment safe. These areas protect plants, animals, and the water from being hurt. Many of these places are watched over to make sure they stay healthy for everything that lives there.

Flora and fauna

See also: Biodiversity of Colombia § Amazon natural region

See also the categories Flora of the Amazon and Trees of the Amazon rainforest

See also: Category:Fauna of the Amazon

The Amazon rainforest is home to many plants and animals. It has more kinds of life than any other tropical forest. The river has many fish, crabs, algae, and turtles.

Mammals

The Amazon River is home to the boto, also called the Amazon river dolphin. It is the largest river dolphin and can grow up to 2.6 m long. The tucuxi is another dolphin in the Amazon. The Amazonian manatee, known as a "seacow", lives only in freshwater. The giant otter is a top hunter in South America.

Reptiles

The anaconda lives in shallow waters of the Amazon. Caimans, which are like alligators, also live there along with many kinds of turtles.

Birds

See also: Category:Birds of the Amazon rainforest

Fish

The Amazon River has the most kinds of fish in the world. Popular aquarium fish like the neon tetra and the freshwater angelfish come from here. The arapaima, one of the largest freshwater fish, can grow very big. The piranha is known for gathering in large groups. The electric eel (Electrophorus electricus) can produce electric shocks to stay safe.

Butterflies

See also: List of butterflies of the Amazon River basin and the Andes

Microbiota

Freshwater microbes in the Amazon are still being studied. Important microbes include Actinomycetota, Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria and Thermoproteota.

Challenges

The Amazon River is very important to many people, but it faces challenges that affect both the environment and local communities. Illegal gold miners have made it hard for the Yanomami, a tribe of about 30,000 people, to protect their land and culture. In 2022, a severe drought caused water temperatures to rise, which hurt many animals in the river. These problems show how important it is to take care of the Amazon and its resources carefully.

Major tributaries

The Amazon River has more than 1,100 tributaries, and twelve of them are longer than 1,500 km (930 mi). Some important ones are:

• Branco
• Casiquiare canal
• Caquetá
• Huallaga
• Putumayo (or Içá River)
• Javary (or Yavarí)
• Juruá
• Madeira
• Marañón
• Morona
• Nanay
• Napo
• Negro
• Pastaza
• Purús
• Tambo
• Tapajós
• Tigre
• Tocantins
• Trombetas
• Ucayali
• Xingu
• Yapura

The longest tributaries are the Madeira River at 3,250 km (2,019 mi), the Purús River at 3,211 km (1,995 mi), and the Japurá or Caquetá River at 2,820 km (1,752 mi). Other long tributaries include the Tocantins River at 2,639 km (1,640 mi) and the Juruá River at 2,400 km (1,500 mi).