I’m applying the four and a half star assignment How It All Began to this webpage. It directs us to detail the conglomeration of a group.
I’ve chosen to describe how the Andean Volcanic Belt, which is composed of the Northern Volcanic Zone, Central Volcanic Zone, and Southern Volcanic Zone, came together.
During the Cambrian Period the Nazca plate started to subduct beneath western South America. This resulted in a continental arc environment known as the Andes Mountains. The Nazca plate’s subduction beneath South America has given birth to three volcanic belts: the Northern, Central, and Southern Volcanic Zones.
The formation of these zones began during the collision of two lithospheric plates. The denser plate, which was the Nazca plate, subducted below the less dense plate. While subducting, the denser plate, which is seafloor, dehydrates over a range of depths up to around 100km releasing aqueous fluids. These fluids are large ion lithophile rich and flow into the overlying mantle wedge, enriching it. Pargasitic amphibole is considered to be the central storage site for water in the hydrated mantle wedge. This mantle wedge is dragged down by the subducting slab where it eventually encounters isotherms which heat it. Being heated, the mantle becomes magma due a depressed melting point derived from hydration. The magma flows upwards becoming more buoyant as crystals fractionate out and decompression melting occurs, furthering its melt content. The extrusion of this magma at the surface of the earth rapidly cools the molten rock. Over time this repeated process created the Andes Mountains.
Part of a test I had a couple weeks ago dealt with continental arc formation. When I read this assignment, the first group to come to mind was the Andes Mountains.