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The Swiss Alps are experiencing a growth spurt, according to a new study suggesting part of the mountain range is rising faster than it is eroding.
The finding goes against the conclusions of two previous studies, which suggested that the Alps were neither growing nor shrinking.
However, an international team of researchers has now found that this was not the case, after analyzing different isotopes, or versions of an element, in the sand of hundreds of rivers in the European Alps. A particular isotope – beryllium-10 (10Be) – revealed information on erosion rates in different parts of the Alps, the team said.
Related: In photos: the endangered glaciers of the European Alps
The 10Be isotope is partially formed when cosmic rays, or fragments of atoms such as protons, electrons and charged nuclei, pass through Earthof atmosphere and reach the surface of the planet. When these cosmic rays hit the ground, say in the rocky Alps, they trigger a nuclear reaction in the oxygen atoms in quartz, which forms 10Be.
This isotope only accumulates on the highest surface of the Earth, which means that scientists can determine the age of a surface by measuring the levels of 10Be in sediments that have been around for at least a few millennia. Quartz grains with a high concentration of 10Be have probably been exposed to cosmic rays for a very long time. In contrast, samples with low concentrations of 10Be are much younger.
“This principle can also be used to quantify the rate of erosion in the Alps, averaged over a few thousand years”, co-author of the study Fritz Schlunegger, geologist at the Institute of Geological Sciences at the University of Bern in Switzerland, said in a press release. In the Alps, rock grains containing 10Be are washed away in mountain streams and rivers, which transport it to the plains. So if a lot of 10Be in fairly low concentration is found in river beds, this suggests newer sediments and in turn that mountains are eroding quite quickly.
In the study, the researchers performed a massive sweep of quartz grains from more than 350 rivers crossing the Alps. “With this strategy, we can for the first time draw a picture of erosion in the whole of the European Alps and explore its driving mechanisms”, studies the first author Romain Delunel, geologist at the Institute of Geological Sciences of the University of Bern in Switzerland. , said in the statement.
Ascent to the sky
However, the Alps do not change in height uniformly. In some places the range is running out. For example, in Valais, a canton (state) in southern Switzerland, the Alps are shrinking, with an erosion rate of nearly 7.5 meters per millennium. The mountainous region with the slowest rate of erosion, in eastern Switzerland by the Thur River, has eroded only 0.5 inch (1.4 cm) per 1000 years.
“This erosion rate is very low, almost annoying,” Schlunegger said.
But the central Alps are developing, thanks to an uplift that exceeds erosion. “It’s a big surprise, because so far we’ve assumed uplift and erosion are in balance,” Schlunegger said. To put a number on it, this region of the Alps grows about 31 inches (80 cm) every millennium, after accounting for erosion, the researchers found. “This means that the Central Alps continue to grow, and surprisingly rapidly,” Schlunegger said.
Meanwhile, erosion and uplift are in equilibrium in the Western Alps, and erosion is faster than uplift in the Eastern Alps.
So why does erosion occur in some parts of the Alps, but not in others? Rain and snow do not have a measurable effect on erosion, unlike the slope and topography of a mountain. Many of these rock faces were sculpted by the last major glaciations, the researchers found. In addition, “very steep landscapes” do not lead to increased erosion, Delunel said. “It was another surprise because we thought very steep terrain would erode very quickly. We are not yet fully sure why this is not the case and therefore see the need for further research.”
The study was published in the December issue of the journal Earth-Science Reviews.
Originally posted on Live Science.
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