New research clarifies how extraordinarily deep canyons formed on the Andean Plateau in Peru. The plateau reaches roughly 3.7 kilometres in elevation, while the valleys that cut into it are 2–3 kilometres deep; the scale is so large that researchers say photographs do not fully convey their size. The study appears in Science Advances.
The research team, led from the University of Pittsburgh with collaborators at the University of Glasgow and first author Jennie Plasterr, used computer models that integrate the region's tectonic history with recent climate and precipitation estimates. Until now, scientists proposed two main explanations: abrupt events such as rapid uplift from earthquakes, or long periods of heavier rainfall increasing river erosion. The models tested both ideas against the landscape.
Results show that neither rapid uplift nor increased rainfall alone explains the deep incision. Both factors contributed, but the dominant mechanism was river capture: when one river erodes across a ridge and diverts a neighbouring river, the capturing channel gains water and erosive force and can cut much deeper. Tectonic activity mattered in a specific way — uplift needed to slow substantially so rivers could cut through ridgelines. The models indicate a slowdown of almost an order of magnitude (for example from 4 mm/yr to 0.4 mm/yr) was necessary for river capture to produce the modern landscape. The study was supported by the National Science Foundation and the German Research Foundation; source: University of Pittsburgh.
Difficult words
- plateau — large flat area of high land
- incision — deep cutting into land by rivers
- river capture — when one river diverts another's flow
- erosion — process of wearing away rock and soil
- uplift — rise of the Earth's surface or land
- slowdown — a decrease in the rate of movement
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Discussion questions
- Photographs do not fully convey the canyons' size. Do you think photographs can effectively show geological scale? Why or why not?
- The article says both climate and tectonics contributed. How might changes in rainfall interact with tectonic activity to change a landscape? Give reasons.
- River capture can change a river's course and power. What effects might such a change have on local ecosystems or human communities?
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