Innovative technology that accurately captures how mountains lean toward raindrops has helped solve a long-held scientific mystery.
The dramatic impact of precipitation on the evolution of mountain landscapes is widely discussed among geologists, but new research led University of Bristol and published today in Scientific achievements, clearly calculates its impact, continuing our understanding of how peaks and valleys have evolved over millions of years.
Its results, which focused on the most powerful mountain ranges – the Himalayas – also pave the way for predicting the possible impact of climate change on landscapes and, in turn, on human life.
Lead author Dr. Byron Adams, a member of the Royal Society of Dorothy Hodgkin, a member of the Cabot University Institute for the Environment, said: “It may seem intuitive that more rain can form mountains, forcing rivers to cut rocks faster. But scientists also believe that rain can blur the landscape quickly enough to essentially “suck” rocks off the Earth, effectively lifting mountains very quickly.
“Both of these theories have been debated for decades because the measurements needed to prove them are so painstakingly complicated. This is what makes this discovery such an exciting breakthrough, as it strongly supports the idea that atmospheric and solid terrestrial processes are closely linked.
While there is no shortage of scientific models to explain how the Earth works, a bigger challenge may be to make good enough observations to verify the most accurate ones.
The study was based in the central and eastern Himalayas of Bhutan and Nepal, as this region of the world has become one of the most selective landscapes for studying the level of erosion. Dr. Adams, along with researchers at the University of Arizona (ASU) and the University of Louisiana, used space clocks in sand grains to measure the rate at which rivers erode rocks beneath them.
“When a space particle from outer space reaches Earth, it is likely to fall into the sand on the slopes of the hills when they are transported to rivers. When this happens, some atoms within each grain of sand can turn into a rare element. By counting how many atoms of this element are present in the sandbag, we can calculate how long the sand has been there, and therefore how quickly the landscape is eroding, ”said Dr. Adams.
“Having obtained erosion indices from the entire mountain range, we can compare them with variations in river steepness and rainfall. However, such a comparison is extremely problematic, as each data point is very difficult to obtain, and the statistical interpretation of all data together is difficult. “
Dr. Adams overcame this problem by combining regression techniques with numerical models of how erosions are destroyed.
“We tested a wide range of numerical models to reproduce the observed pattern of erosion rates in Bhutan and Nepal. In the end, only one model was able to accurately predict the measured erosion rates, ”said Dr. Adams.
“This model allows us, for the first time, to quantify how precipitation affects the rate of erosion in rough terrain.”
Researcher Professor Kellin Whipple, a professor of geology at ANU, said: “Our findings show how critical it is to consider precipitation when assessing the patterns of tectonic activity using topography, and provide an important step forward in how fast sliding tectonic faults can be controlled. climatic erosion on the surface “.
The study also has important implications for land management, infrastructure maintenance and hazard in the Himalayas.
In the Himalayas, there is a constant risk that high erosion rates could dramatically increase sedimentation behind dams, jeopardizing critical hydropower projects. The findings also suggest that more rainfall could blow up hillsides, increasing the risk of debris flows or landslides, some of which could be large enough to dam the river, creating a new danger – floods from lake outbreaks.
Dr Adams added: “Our data and analysis provide an effective tool for assessing erosion patterns in mountainous landscapes such as the Himalayas and can therefore provide an invaluable insight into the dangers affecting hundreds of millions of people living in and at the foot of these mountains. “.
The research was funded by the Royal Society, the British Council for the Environment (NERC) and the National Science Foundation (NSF).
Based on this important study, Dr. Adams is now studying the reaction of landscapes after large volcanic eruptions.
“This new frontier in modeling landscape evolution is also shedding new light on volcanic processes. With our advanced methods of measuring erosion rates and rock properties, we can better understand how rivers and volcanoes have affected each other in the past, ”said Dr. Adams.
“It will help us more accurately predict what is likely to happen after future volcanic eruptions and how to address the consequences for nearby communities.”
For reference: October 16, 2020, Scientific achievements.