Southern Chile and Argentina
The rugged, snow-capped Andes dominate the left side of this image of Southern Chile and Argentina.
The Andes measure approximately 7000 kilometers (4400 miles) long and 500 kilometers (300 miles) wide and range along the West coast of South America. The light-colored landscape at the top of the image are the rich, fertile plains or Pampas, while the darker colored landscape near the bottom is the Patagonia region.
The Andes are young in geologic time as they started to form only about 200 million years ago; in contrast, the Appalachians in the Eastern United States are almost 700 million years old. The mountains were formed along the boundary where two plates collided, creating what is called a "subduction zone".
The denser, oceanic Nazca Plate which underlies the Pacific Ocean is being pushed under the lighter continental South American plate; it is actually sinking into the mantle, the area in between the Earth's crust and core. This results in a geologically active region, prone to volcanic activity and severe earthquakes.