Why are the Andes Mountains abnormally tall?

A paper in Nature Communications, led by former graduate student Jiashun Hu and Professor Lijun Liu, provides a new explanation for why the Andes mountains are so tall.

Date

12/20/21

In a new paper in Nature Communications, former graduate student Jiashun Hu (now at the Southern University of Science and Technology, Shenzhen, China), Professor Lijun Liu and California Institute of Technology professor Michael Gurnis, show how the interactions between sediment flux, climate and tectonics can explain the anomalously tall central region of the Andes Mountains. Oceanic subduction zones have relatively low compressional stresses relative to continental collision zones due to the weak plate interface coupling where thin, dense oceanic crust is subducted. The question is thus: why are the Andes so tall?

Prof. Lijun Liu
Prof. Lijun Liu

 

The paper proposes that the Juan Fernandez Ridge, which intersects the coast of Chile (see figure), acts as a barrier to northward-migrating sediments. This ridge has existed for millions of years, slowly migrating southward with the subducting Nazca Plate, and has thus starved the northern Andean Trench of sediments. Because the thickness of trench-fill sediments is a proxy of plate coupling, with less sediment accumulation causing stronger coupling, relative starvation of sediment north of the Juan Fernandez Ridge thus helps increase plate coupling and mountain building behind the migrating ridge. The study shows the power of combining modern top-down models that account for climate-related factors with traditional bottom-up tectonic models, for uncovering the history of the Andes Mountains.

See here for the full News Bureau story and here for the Nature Communications paper.

 

3D-relief map illustrating how the submerged east-west trending Juan Fernandez Ridge may act as a barrier to northward-migrating trench sediments. The Juan Fernandez Ridge is part of the oceanic Nazca Plate (left) that is subducting under the South American continental plate (right).
3D-relief map illustrating how the submerged east-west trending Juan Fernandez Ridge may act as a barrier to northward-migrating trench sediments. The Juan Fernandez Ridge is part of the oceanic Nazca Plate (left) that is subducting under the South American continental plate (right).