The Amazon River is one of longest and largest rivers in the world. It is also an ancient river; the Amazon started 11 million years ago as a transcontinental river and took on its current form around 2.4 million years ago. Coursing through the most biologically diverse biomes in the world, the Amazon is a critically important river system. Here are some interesting geographical facts about the Amazon River.
The Amazon River located in South America is the world’s second longest river. At 3,976 miles (6,400 km) in length, it only narrowly loses the title for the world’s longest river to the Nile River in Egypt, which is 4,132 miles (6,650 km) in length. The Amazon River is the largest in terms of drainage and waterflow. The Amazon River has an average discharge of roughly 7,381,000 cubic feet per second (209,000 cubic meters per seconds) with an outflow into the Atlantic Ocean. This discharge is greater than the next seven rivers combined. The Amazon also has the largest drainage basin in the world at 2,720,000 square miles (7,050,000 square kilometers), and accounts for one-fifth of the world’s total river flow.
The vast width of the Amazon has earned it the nickname, The River Sea. The width of the Amazon varies greatly. During the low season, the river ranges from one to 6.2 miles in width. During the wet season, the Amazon expands to widths of 30 miles (48 kilometers). Flooding usually occurs between June and October. Flowing through South America, the countries of Brazil, Peru, Bolivia, Colombia, Ecuador, Venezuela, Guyanaare in its catchment basin. The Amazon Basin covers 40 percent of South America and is the largest in the world.
The Amazon River originates from a glacial stream from a peak, called Nevado Mismifound an elevation of 18,363 feet (5,597 meters) in the Peruvian Andes. A simple wooden cross on the peak marks the most distant source of the Amazon River. The Amazon River region is composed of Precambrian fragments. The Sierra de Carajás, in the Central Amazon province is the most important mineral province in Brazil. Its “greenstone belts” are about 3 billion years old, and represent the oldest rocks in the Amazon craton. (Phyorg.com).
During the Proterozoic, the main Amazon River flowed from east to west, emptying into the Pacific. Its source was in present day Africa. After the collapse and the opening of the Atlantic during the Mesozoic, the South American Plate moved westward, where the Pacific Plate collided with Nazca, a region in the southern coast of Peru (Ward, P. 1995) This collision lifted the Andes and interrupted the flow of the Amazon to the Pacific. Subsequently, large lakes were formed in the eastern part of the Andes, including the Belterra. A slight inclination of the South American continent to the east, led to the reversal of the course of the Amazon toward the Atlantic. During the Cenozoic, the Amazon and its tributaries, gradually carved a basin of the Amazon and today comprises plateaus, plains and valleys.
The Great Barrier Reef, which extends for over 2,300 kilometers (1429 miles) along the northeastern coast of Australia, is home to over 9,000 known species. There are likely many more—new discoveries are frequently being made, including a new species of branching coral discovered in 2017. This richness and uniqueness make the reef crucial for tourism and the Australian economy—it attracts at least 1.6 million visitors every year. Yet the reef’s true value, its biodiversity, extends far beyond dollars and cents.
The Great Barrier Reef consists of about 3,000 individual reefs of coral, and the biodiversity they contain is remarkable. There are animals you would probably recognize, such as dolphins, turtles, crocodiles, and sharks. There are also venomous sea snakes, brightly colored worms, and large algae. These species interact to form a complex and delicate ecosystem dependent on the coral reef for survival. Yet today the coral—and therefore all the organisms that depend on it—is gravely at risk.
Coral is made up of many small animals. These tiny animals build a hard external skeleton to make the vibrant structures that we recognize. When healthy, coral has a symbiotic relationship with algae. The coral produces fluorescent chemicals that protect the algae from bright sun—almost like a sunscreen. The algae use photosynthesis to harness solar energy to make sugars. In this way, the algae provide food and oxygen (a byproduct of photosynthesis) for the coral, and the coral protects and provides nutrients for the algae. The algae also give coral its many colors.
The coral and algae have evolved together to survive within a particular temperature range. As sea temperatures rise due to climate change, the algae begin to produce products toxic to the coral, which in turn expel the algae. This process is called bleaching because the coral becomes white. A 2018 study showed that about one-third of the Great Barrier Reef had experienced substantial damage from bleaching. The researchers also found that large amounts of coral had died in the warming water almost immediately—even before there was time to expel their algal partners. This suggests even greater risks from climate change than scientists had previously thought.
Climate change is not the only threat to the reef. Chemical runoff and other forms of pollution, coastal development, and overfishing all can harm coral and reduce biodiversity. So can large storms such as cyclones. Species that live in the reef can also cause damage. One major pest species is the crown-of-thorns starfish (Acanthaster planci). A starfish may sound harmless, but these venomous creatures voraciously eat coral. Every so often, their numbers spike. Some scientists think these starfish caused over half of the reef damage from 1985 to 2012.
Fortunately, many people are passionate about protecting the Great Barrier Reef. National Geographic Explorer Dr. Erika S. Woolsey conducts research on coral reefs. Dr. Woolsey is the CEO of the nonprofit organization, The Hydrous. (The adjective hydrous means “containing water.”) Woolsey and her colleagues use virtual reality to create 3D versions of specimens that can be viewed in a laboratory. Scientists can see damage to the reef over time and take detailed measurements of every nook and cranny—without having to get wet! People around the world can access images of reef structures to study, thereby contributing to our knowledge of the reef.
So, is there still hope for the Great Barrier Reef? People are making a determined effort to help, and there are things that you can do right at home. Because climate change is an important cause of damage to the reef, efforts to fight it matter. In 2015, 195 countries signed the Paris Climate Agreement, committing to work to reduce carbon emissions and taking other steps to address climate change. You can contact your representatives in Congress to urge the United States to rejoin the Paris Climate Agreement.
You can also make changes in your own life to use less energy, produce less waste, choose environmentally friendly products, and be informed. Even your diet can make a difference: eating locally sourced foods that don’t have to be shipped to your neighborhood reduces carbon emissions. You can even be a citizen scientist and collect data for scientists if you visit the reef.
In a 2017 presentation, Dr. Woolsey explained why it is so important to protect reefs: “Coral reefs . . . provide food and livelihoods for hundreds of millions of people around the world, they protect shorelines from erosion, and they contain compounds that are used to treat human ailments. . . . Even though they cover less than one percent of the sea floor, they harbor about a quarter of all marine biodiversity.”
