Rivers may seem as old as hills, but like anything else in nature, they have a life cycle. Many grow, leaving a meandering mark on the landscape, and eventually die. However, some rivers last longer than others. So which is the oldest river in the world today?
The winner is older than the dinosaurs. Australia’s Finke River, or Larapinta River in the indigenous Arrernte language, is between 300 and 400 million years old.
you may like
One of the strongest pieces of evidence for its antiquity is a geological anomaly called transaxial drainage, said Victor Baker, a geomorphologist at the University of Arizona. Rather than flowing parallel to resistant rock structures such as quartzite, the Finke River traverses these hard mineral formations as it passes through the MacDonnell Ranges of central Australia.
Because water always takes the easiest path, it is counterintuitive that rivers flow toward hard rocks rather than along them. The existence and origin of drainage across this axis therefore reveals important details about the historical course of the Finke River.
“There is some suggestion that pre-existing drainage was flowing as this area expanded,” Baker told LiveScience. “This is called an antecedent phenomenon. Basically, the rivers were there before the mountains were formed, and as the crust is pushed up, the rivers are carved away.”
The MacDonnell Ranges (also known as Chorica in Arrernte) were formed as part of the Alice Springs Orogeny (a tectonic mountain building event that occurred between 300 and 400 million years ago), and the Finke Ranges are at least as old as these ranges.
Subsequent evidence comes from erosion and weathering, which produce specific chemical profiles. This information shows how and where the surface interacted with the atmosphere and water flows over time. Scientists can also use the radioactive signature of certain isotopes (elements with different numbers of neutrons in their atomic nuclei) to infer the ages of these rocks. Because radioactive isotopes decay at a constant rate, it is possible to estimate when a rock was formed by calculating backwards from the relative proportions of various isotopes. Combining these data points creates a roadmap for piecing together the history and evolution of the Finke River.
However, rivers are constantly changing, with some growing larger each year and others drying up completely. So why did the Finke regime last so long?
“Rivers can disappear if a large input of sediment overwhelms them (e.g., a volcanic eruption), or if the landscape changes so dramatically that flowing water takes a new course across the landscape (e.g., advancing and retreating glaciers),” Colorado State University geologist Ellen Wall told LiveScience in an email.
you may like
Additionally, “climate change and human consumption of water could cause rivers to stop flowing,” Wall said. “The stability of the Earth’s crust and the lack of glaciers during the Pleistocene (2.6 million to 11,700 years ago) led to a longer lifespan.”
For the Finke people, Australia has had an unusually stable landscape for a very long time. The continent, located in the middle of the Australian plate, has experienced virtually no significant tectonic activity in the past hundreds of millions of years, Baker explained. As a result, the Finke River system was able to develop and expand with little interruption for most of its history.
As for the future, it is difficult to say how long Finke will continue as coach.
“Long lasting [rivers] That’s probably going to continue,” Wall said. However, “many dryland rivers” such as the Finke have been “significantly altered by human water consumption”.
He added: “This amount is likely to increase in the future as global water consumption continues to rise and global warming is making many arid regions even drier.”
If the Finke River dries up, Baker said the runner-up could be the New River. The river dates back about 300 million years and currently flows through Virginia, West Virginia, and North Carolina.
What’s Inside the Earth Quiz: Test your knowledge about Earth’s hidden layers
Source link
