Brecheisen Week 5 Nazca-South America Converging Plates

This week I took a trip to South America to visit the Andes Mountains. I had to travel from the northern coast of Venezuela down to the southern coast of Argentina to fully explore the vast range of the Andes. The mountain range stretches for 8,900 kilometers and is the longest mountain range in the world. It also consists of some of the highest peaks in the world, including the highest peak in the Western Hemisphere, Mount Aconcagua.

This impressive range was created during an oceanic-continental convergence as a result of the Nazca oceanic plate subducting beneath the South American continental plate. This happened because the Nazca plate was denser than the buoyant lithosphere of South America. The two deformations that resulted from this convergence are the Andes continental arc and the Atacama trench. Since the Andes were formed by oceanic-continental convergence, they are actually a volcanic belt. The structure of the South American Plate is folded during convergence, thickening the crust while reducing the width of the lithosphere. This folding is what produced the Andes Mountains.

Because the Andes were formed by oceanic-continental convergence, they are an example of a reverse fault. This is characterized by the hanging wall rising relative to the footwall. The stress involved with this type of fault is compressive. This is caused by the two plates compressing against each other and essentially squeezing the terrain into a reverse fault. As the oceanic plate converges with the continental plate, some of the ocean floor sediments are scraped off onto the South American plate during a process known as obduction. This results in a wedge of layers of deformed and metamorphosed sediments.

The Andes Mountains were already an impressive mountain range, but learning how they were formed makes them that much more interesting. It’s wild to think that an oceanic plate converging with a continental plate could create such a large mountain range. It would take more time than I have to fully explore this mountain range and these high peaks, but that just means I can come back again and always have someplace new to see.

References

The Geological Society. Retrieved from https://www.geolsoc.org.uk/Plate-Tectonics/Chap3-Plate-Margins/Convergent/Oceanic-continental

Stewart, N., Denevan, W., & Velasquez, M. (2017). Andes Mountains. Retrieved from https://www.britannica.com/place/Andes-Mountains/The-people