Week 5 - Converging Plates

In my South American travels, I had the privilege of witnessing the effects of converging plate boundaries. While traveling along the western coast of Peru, the signs of an ocean-continent plate convergence are unmistakable. One big sign, though not immediately visible, is the massive Peru-Chile Trench, also known as the Atacama Trench.

Red line shows the Per-Chile Trench
http://googlesadi.blogspot.com/2011/04/peru-chile-trench-map.html

 This trench spans 3,666 miles, coving almost the entire western coast of South America and reaches depths of nearly 26,500 feet. This trench is caused by the subducting of the oceanic lithosphere of the Nazca plate under the continental lithosphere of the South American plate. The more immediately noticeable effect of these converging plates is the formation of the Andes mountain range. Like the Peru-Chile Trench, this mountain range spans much of the western edge of the South American continent, covering a distance of about 5,500 miles. The Andes mountain range is a result of the compression caused by the two converging plates. Though the compression is not as great as that found in continent-continent convergence, it is still enough to this stunning mountain range. Yet more evidence of the plate activity in this region is the existence of over 25 volcanos along the plate boundary. This volcanic activity is brought on by seawater that goes under the South American plate during subduction. This water heats up, rises through the crust and lowers the melting point of the rock allowing for partial melting. This then produces pockets of magma that is less dense than the surrounding rock allowing it to rise, eventually bringing about the volcanic activity that we see.

Brown area shows the Andes Mountain range
http://ourweddingvideo.us/andes-mountains-map.html