6400 km of water reversed: what caused the world's largest river to change course

The Amazon is the largest river in the world in terms of water volume and catchment area. Its length is approximately 6,400 kilometers, and it begins in the Andes, passes through Peru, crosses South America, and flows into the Atlantic Ocean.

This is reported by IFLScience. About 20 years ago, Russell Mapes, a graduate student geologist at the University of North Carolina, tried to study the movement of sediments from the Andes to the Atlantic. During his research, he made an extraordinary discovery.

While studying sediments in central South America, the scientist discovered ancient particles of zircon, a precious stone that could only have come from the east, not from the young Andes located in the west. According to Mapes, the age of the mineral grains in the river basin pointed to specific locations in central and eastern South America. This came as a surprise because the Amazon now flows from west to east, not the opposite direction. So what could have moved these ancient zircon deposits from east to west?

The researchers emphasize that this is not the only evidence that indicates that the river once flowed in the opposite direction. In particular, fossils of marine organisms accustomed to water were found in places where scientists did not expect to find them.

After further research, scientists have found that millions of years ago, the Amazon really did flow in the other direction. They attribute the change in flow direction to the formation of highlands in northeastern South America, which was formed during the Cretaceous period, approximately between 65 and 145 million years ago.

According to the team leader, Drew Coleman, the reason for the change in the river's direction is that the Amazon has such a slight slope that even minor changes can lead to significant changes in the channel. The researchers suggest that even before the formation of the Andes, this gradient could have forced the river to flow from east to west, toward the Purusa Arch, while the water in the west of the arch was headed toward the Pacific Ocean. However, when the highlands in the northeast began to erode, the river began to flow in the opposite direction.

Scientists also found that over time, as the Andes mountains rose, a basin formed between the mountains, which filled with water and eventually spilled out, leading to a change in the direction of the river as we know it now.

The team believes that the last change in direction occurred about 5-10 million years ago, which is a relatively rapid process from a geological perspective. Mapes emphasized that this is further evidence of how variable the surface of our planet is.

In 2014, based on a new model, scientists suggested that the rise of the Andes caused more clouds to remain on their peaks, which in turn caused heavy rainfall and erosion, resulting in the Pebas wetlands. Subsequently, the accumulation of precipitation raised the area, which led to a change in the direction of the Amazon's flow.

The researchers hope that further studies will reveal the mechanism that made such a huge river change its direction.

If you want to get the latest news about the war and events in Ukraine, subscribe to our Telegram channel!