The origin of the Andes unravelled

December 11, 2017

Why do the Andes exist? Why is it not a place of lowlands or narrow seas? Wouter Schellart, a geophysicist at the Vrije Universiteit Amsterdam, has been pondering these questions for more than a decade. Now, he has found the answers using an advanced computer model. "It's a matter of enormous size, longevity and great depth", he said. "These aspects made the Andes the longest and second-highest mountain belt in the world."

All the other major mountain belts on Earth, such as the Himalaya and the Alps, were formed due to colliding continents. But there are no colliding continents in the Andes; rather, the Andes are located at a so-called subduction zone, a place where an oceanic tectonic plate sinks below another plate (in this case the Nazca plate sinking below the South American plate) into the Earth's interior, the mantle. There are numerous other subduction zones on Earth, such as in Greece and Indonesia, but these locations are characterized by small seas (such as the Aegean Sea) and tropical lowlands, not massive mountain chains. So the big question is: Why did a massive mountain chain form in South America?

Andean evolution

Schellart's model, which took more than two years to complete on Australia's supercomputer Raijin, has reproduced the evolution of the South American subduction zone, from start to present (initiating some 200 million years ago and thereby the oldest subduction zone in the world), to investigate the origin of the Andes. What came out? The size of the subduction zone, some 7000 km and thereby the largest in the world, is crucial for mountain building. What else came out? The first signs of crustal shortening and mountain formation started already in the mid Cretaceous, some 120-80 million years ago. Before this time there were elongated narrow seas at the western edge of South America rather than mountains. Form the mid Cretaceous onwards the subduction zone was deep enough to induce large-scale flow in the deep mantle, down to 2900 km, the boundary between the Earth's mantle and core.

These flows dragged South America westward, causing the continent to collide with the subduction zone and thereby forming the Andes. Because the South American subduction zone is so wide, it provides much resistance to migrate laterally, in particular in the centre. This is why the collisional forces between the South American continent and the subduction zone are largest in the centre, resulting in the highest mountains in the Central Andes and formation of the Altiplano, a high plateau at 4 km above sea level, but much lower mountains in the north and south.

Read more about this research in Nature Communications

Vrije Universiteit Amsterdam

Related Subduction Zone Articles from Brightsurf:

The connectivity of multicomponent fluids in subduction zones
A team of researchers has discovered more about the grain-scale fluid connectivity beneath the earth's surface, shedding new light on fluid circulation and seismic velocity anomalies in subduction zones.

Distinct slab interfaces found within mantle transition zone
Prof. CHEN Qifu's group from the Institute of Geology and Geophysics, Chinese Academy of Sciences (IGGCAS) and their collaborators observed two distinct seismic discontinuities within the mantle transition zone (~410 km to 660 km) beneath the western Pacific.

New fault zone measurements could help us to understand subduction earthquake
University of Tsukuba researchers have conducted detailed structural analyses of a fault zone in central Japan to identify the specific conditions that lead to devastating earthquake.

A review of ridge subduction, magmatism and metallogenesis
Ridge subduction events are very common and important geodynamic processes in modern oceanic plate tectonics (Figure 1), and play an important role in the generation of arc magmatism, material recycling, growth and evolution of continental crust, deformation and modification of overlying plates and metallogenesis.

Is the Earth's transition zone deforming like the upper mantle?
In a recently published paper in Earth and Planetary Science Letters, researchers from the Geodynamics Research Center, Ehime University and the University of Lille combine numerical modeling of dislocation glide and results from diffusion experiments to revisit the rheology of wadsleyite, ringwoodite and majorite garnet under geological strain rates across the transition zone of the Earth's mantle based on theoretical plasticity modeling.

Scientists review the metallogenesis and challenges of porphyry copper systems above subduction zone
Porphyry copper ± molybdenum ± gold deposits (PCDs) are the most economically important magmatic-hydrothermal metallogenic system above subduction zones, which have supplied nearly 3/4 of the world's copper, 1/2 of the molybdenum and 1/5 of the gold, as well as large amounts of silver, zinc, tin and tungsten, with however their metallogenesis remaining controversial.

Does accelerated subduction precede great earthquakes?
A strange reversal of ground motion preceded two of the largest earthquakes in history.

Badger behavior inside the cull zone
A study led by researchers at international conservation charity ZSL (Zoological Society of London) and Imperial College London has found that culling drives badgers to roam 61% further afield -- helping to explain why the practice, intended to reduce bovine TB transmission, can sometimes exacerbate the problem instead

A Goldilocks zone for planet size
Harvard University researchers described a new, lower size limit for planets to maintain surface liquid water for long periods of time, extending the so-called Habitable or 'Goldilocks'' Zone for small, low-gravity planets.

Water detected on an exoplanet located in its star's habitable zone
An international study lead by UdeM astronomer Björn Benneke has detected water vapor on the planet K2-18b; this represents a major discovery in the search of alien life.

Read More: Subduction Zone News and Subduction Zone Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to