A small part of the Finke River in Australia
The oldest river in the world predates the dinosaurs. But how does science know this?
O rio Finke (or River Larapinta in the indigenous language is arrink), in Australia, is between 300 million and 400 million years old.
This network of watercourses and canals extends across more than 640 kilometers.
Arid conditions in the center of the continent mean that the river flows only intermittently; for most of the year it exists as a sequence of isolated pools of water. However, a combination of geological records, weather profiles and measurements of radionuclides in the surrounding sediments and rocks allowed scientists to date this river system to the Devonian (419 million to 359 million) or Carboniferous (359 million to 299 million) period.
As he explained to , Victor Bakergeomorphologist at the University of Arizona, one of the strongest evidence of its ancient age is a geological anomaly called drainage across the axis.
As the same magazine details, instead of flowing parallel to resistant rock structures such as quartzite, the Finke River cuts through these hard mineral formations as it crosses the MacDonnell Ranges in central Australia.
Here, the running water always choose the easiest pathwhich makes it counterintuitive for a river to flow against these hard rocks rather than along them. Consequently, the presence and origin of this axis-cross drainage reveal crucial details about the historical course of the Finke.
Peculiar geomorphology proves theory
The MacDonnell Ranges formed as part of the Alice Springs Orogeny — a mountain-building tectonic event that occurred 300 million to 400 million years ago — making the Finke at least as old as these mountains.
Others evidence comes from erosion and weatheringwhich generate specific chemical profiles. This information indicates how and where the surface interacted with the atmosphere and water runoff over time.
Using the radioactive signatures of certain isotopes (elements with different numbers of neutrons in their nuclei), scientists can also infer the ages of these rocks. Because radioactive isotopes decay at a fixed rate, it is possible to estimate when rocks formed by looking back from the relative proportions of different isotopes. Together, these data points create a roadmap for reconstructing the history and evolution of the Finke River.
But rivers are constantly changing, with some growing from year to year and others drying up completely. “So why did Finke’s system last so long?” – asks Live Science
“Rivers can disappear if a huge influx of sediment overloads them (such as volcanic eruptions) or if the topography changes so dramatically that the flowing water adopts a new route across the landscape (for example, glacial advance and retreat)”, he explained to the magazine, Ellen Wohlgeologist at Colorado State University.
“In addition, rivers may stop flowing due to climate change and/or human use of water. The long duration is favored by tectonic stability and the absence of glaciation during the Pleistocene” [há 2,6 milhões a 11 700 anos]”, he added.
In Finke’s case, the Australia has been an unusually stable landscape for a long time. Located in the middle of the Australian Plate, the continent has experienced virtually no significant tectonic activity in the last several hundred million years, Baker explained.
Consequently, the Finke River system has been able to develop and expand almost without interruption for most of its history.
The second oldest river in the world is the rio Newwhich runs through Virginia and North Carolina, in the USA. It is about 300 million years old
