Week Four – Converging Plates

Week Four – Converging Plates

Today the family visited the Andes Mountain Range.  The Andes Mountain Range is the largest mountain range that is over 5,500 miles long.  They extend from the southern tip of South America to the north coast by the Caribbean Sea.  The mountain range has high plateaus surrounded by higher peaks.  These peaks are some of the highest in the Western Hemisphere.  The highest one is Mount Aconcagua, which stands at 22,831 feet tall.  The peaks, depressions, and plateaus run mostly in a north and south direction (Denevan, Velasquez, & Stewart, 2017). 

The mountain range is the result of the collision of the South American Plate and the Nazca Plate.  The process began 450 to 250 million years ago.  The sediment that accumulated on the western side of the Brazilian shield weighted the shield down and displaced the crust downward.  The increase in temperature and pressure changed the sandstone, siltstone, limestone into quartzite, shale, and marble.  Then around 170 million years ago the Nazca Plate (ocean plate) was compressed under the South American Plate (continental plate).  During this process a lot of volcanic activity happened, magma intruded this process and as a result a concentration of many valuable minerals can be found in the Andes (Denevan, Velasquez, & Stewart, 2017).  Because of the low density and thickness of the crust much of the magma was trapped beneath the crust and huge batholiths were created (Lutgens & Tarbuck, 2015) (p. 305).  Then around 25 million years ago the rocks and minerals began to be pushed up and create the mountain range called the Andes.  This convergent plate is considered to be part of the Pacific volcanic chain called the Ring of Fire and is still active with potentially very damaging earthquakes (Denevan, Velasquez, & Stewart, 2017).

The Andes Mountain Range is made up of many different types of rocks.  These sedimentary rocks include sandstone, siltstones, shales, limestone, and quartzites.  The eastern range contains many low-angle thrust faults.  It also includes valuable minerals that are mined including tin-silver, gold, and lead-zinc-silver belts.  The highest peaks are massive intrusive closely grouped made mainly of granodiorite (Andeansummits, n.d.).  

                             South face of Aconcagua, 22,841 feet (Zimmermann, 2013).

                       Machu Picchu built into the Andes (Newworldencyclopedia, 2016).

                                           
                                                                     References

Andeansummits. (n.d.). Geological history of the Andes. Retrieved from https://www.andeansummits.com/geological-history-andes

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

Lutgens, F. & Tarbuck, E. (2015). Essentials of Geology (12^th ed.). Upper Saddle River, NJ: Pearson Education, Inc.

Zimmermann, K. (2013). Andes: World’s Longest Mountain Range. Retrieved from https://www.livescience.com/27897-andes-mountains.html

          Newworldencyclopedia. (2016). Andes. Retrieved from 
           http://www.newworldencyclopedia.org/entry/Andes