Regis University Science Travel Journal: Week 5: The Volcanic Andes and Converging Plates

Sunday, April 14, 2019

Week 5: The Volcanic Andes and Converging Plates

While exploring and visiting South America, there are certainly numerous attractions and sites to visit, but one picturesque feature is very hard to miss, especially because it stretches for about 7,000 kilometers across seven countries nearly along the entire western edge of South America - the Andean Mountains! The Andes are longest continental mountain range in the world, and hasan average height of about 4,000 meters - the range is so long that it's divided into several smaller ranges.

The Andean Mountain Range Map (via WorldAtlas)

While doing some hiking in the valley city of La Paz in Bolivia, which is surrounded by mountains and amazing hiking trails and challenges, we often wondered how this mountain range came to be. After some research, it turns out that the Andes are a result of a convergent plate boundary between the Nazca Plate and the South American Plate, where the mountain range rises as the South American Plate causes compression from the subduction of the Nazca Plate. Subduction occurs at convergent boundaries of tectonic plates like these, where one plate (the Nazca Plate) moves under another (the South American Plate) and is forced to underneath, causing a subduction zone on the surface that leads to volcanism and earthquakes, as well as deformation and plate collision that causes mountains, like the Andes, to rise.

Oceanic and Continental Convergent Plate Boundary Process for the Andes (via The Geological Society)

As the layers of deformed ocean sediment and crust is forced onto the South American Plate along faults (called the accretionary wedge in the image above), folding occurs in the rocks that are being pushed and compressed, creating new mountain range. Additionally, the subduction creates partial melting of the mantle, which can then produce andesitic magma to cause explosive volcanic activity, such as with the Láscar volcano in northern Chile, which last erupted in 1993. In fact, the Andes currently has more than 150 potentially active volcanoes because of this mixture of convergence boundaries and the level of subduction occurring along these plates.

The Andes Volcanic Belt (via Americas Tectonics)

All of this together has created the beautiful fold mountains and landscapes that we see all along the Andes, stretching so far that it'll take multiple trips to South America just to see some of it!