Falling rocks in mountains can pose a serious threat to mountaineers, roads and railways. When, where and how many rocks detach from their mountain partially depends on the climate. As the climate is warming, how will that influence rock falls and mountain erosion in the future? An international team of researchers led by Utrecht University’s Daniel Draebing looked into the past to find an answer.
Stabilising mountains
Similar to how ice creates cracks in roads, when water in mountains expands as it freezes, it can break off rocks. At the same time, permafrost ice - water that has been frozen for over two years - acts like concrete, stabilising the mountains. When permafrost ice and glaciers melt because of a warming climate, this makes the mountain slopes instable and prone to erosion.
Over millennia, mountain slopes stabilise.
Dr. Daniel Draebing
Short or long term
In the short term, this means that a warming climate increases the risk of falling rocks. "However," Daniel Draebing, assistant professor at Utrecht University and lead author of the new study says, "Over millennia, as the mountains freeze less and break down less often, the mountain slopes stabilise and erode much slower."
Draebing and his colleagues reconstructed freezing and thawing conditions, as well as current and past mountain erosion in Hungerli Valley, a small alpine valley in Southern Switzerland. "When mountains just become free of ice, permafrost and glaciers, we found that erosion was very high," Draebing says. "But slopes that are already ice-free and seldom froze, there wasn’t much erosion."
A look into the future
Climate change induced warming is now exceeding the warming the Earth has experienced in the past 11,000 years. Freezing temperatures along with glacier and permafrost ice retreat higher and higher up the mountain until mountains peaks are reached. "In the near future, we can expect more mountain erosion which threatens infrastructure such as cable cars or mountain huts, at least until ice and freezing conditions have disappeared," Draebing concludes.
Publication
Daniel Draebing, Till Mayer, Benjamin Jacobs, Steven A. Binnie, Miriam Dühnforth, Samuel T. McColl, Holocene warming of alpine rockwalls decreased rockwall erosion rates (2024), Earth and Planetary Science Letters, Volume 626, 2024, https://doi.org/10.1016/j.epsl.2023.118496 .
