Researchers examined why massive canyons cut into the Andean Plateau in Peru. The plateau stands at about 3.7 kilometres elevation and the canyons are 2–3 kilometres deep; by comparison the Grand Canyon is under 2 kilometres at its deepest point. Photographs, researchers say, do not fully show their scale.
The team included Nadine McQuarrie of the University of Pittsburgh, collaborators at the University of Glasgow and first author Jennie Plasterr. Their work appears in Science Advances. They ran computer models that combine the known tectonic history of the region with recent estimates of climate and precipitation.
The models found that neither abrupt uplift nor increased rainfall alone caused the valleys. Both helped, but the main driver was river capture: one river cutting across a ridge diverts a neighbor and gains extra flow and erosive power. Crucially, uplift had to slow by almost an order of magnitude — for example from 4 mm per year to 0.4 mm per year — so rivers could breach ridgelines and incise deeply.
Difficult words
- plateau — A large flat area of high land
- canyon — A deep narrow valley with steep sidescanyons
- tectonic — Related to movements of the Earth's crust
- precipitation — Any form of water that falls from clouds
- river capture — When one river takes the flow of another
- uplift — A rise of land surface over time
- incise — To cut into rock or soil by water
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- Do you think river capture is easy to see in modern landscapes? Why or why not?
- Which matters more for creating big valleys where you live: climate (rainfall) or changes in the land (uplift)? Explain briefly.
- How could photographs fail to show the full scale of a landscape like the Andean canyons? Give one reason.
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