Editing Andes (section)

== Geology ==
The Andes formed through the movement of oceanic crust beneath the western edge of the South American Plate. Along most of the continental margin, the Nazca Plate descends beneath South America. Compression above the plate boundary shortened and thickened the continental crust, causing it to rise. This process began before the modern range developed and continues to affect the mountains.

Subduction also produces earthquakes and volcanic activity. Magma rises where water released from the descending plate lowers the melting point of the overlying mantle. The resulting volcanoes occur in distinct sections rather than as an uninterrupted chain because the angle of the descending plate changes along the continent.

Erosion has reshaped the uplifted terrain. Rivers cut through the eastern slopes and carry sediment toward the continental interior. Glaciers widened valleys in the southern Andes and left moraine deposits after retreating. Tectonic activity also contributed to the formation of mineral deposits. Copper mining became especially extensive in Chile, while highland basins in the central Andes contain lithium-bearing salt deposits.