Friday, April 24, 2015

Andes Volcanism

The eruption of the Calbuco Volcano in southern Chile this week is that peak's first significant activity since 1972 and the most recent eruption in the Andes Chain, a volcanic range that began to form during the Mesozoic Era (the Age of Dinosaurs).  As Pangea broke apart and the Atlantic Ocean began to open (some 150 million years ago), the North and South American Plates were shoved westward, a tectonic process that continues today.

Along the western edge of the Americas, the oceanic Farallon Plate was forced to subduct beneath the advancing continental masses.  Now represented by smaller remnant plates (the Juan de Fuca, Cocos and Nazca Plates, north to south), the eastern edge of the subducting oceanic plate melted (and continues to melt) beneath the western edge of the American Plates, producing the Cascades, the Mexican and Central American Volcanic Belt and the Andes, respectively.  In southernmost South America, the Antarctic Plate is subducting beneath South America, producing the southern tip of the Andes Chain.

The Andes, stretching 4300 miles from Colombia to southern Chile, harbor the highest volcanic peaks on the planet (many exceeding 22,000 feet in elevation).  While volcanic activity continues in all subduction zones of the Americas, the large number of volcanic peaks in the Andes ensures that the majority of events occur in that range.  Of course, these subduction zones are also prone to earthquakes and tsunamis, triggered by the release of pressure between the subducting and over-riding plates.