Week 5 - Plate Boundaries - Tracey P

This week's travels take me to the tallest mountains in the Western Hemisphere, the Andes Mountain Range on western South America. The Andes are formed by the converging of the Nazca and South American plates. Specifically, the subduction of the Nazca plate UNDER the South American Plate.

Graphic of the Nazca Plate, WikiCommons

The Nazca plate movement is the fastest moving plate (in absolute terms) of Earth's crust, moving at an impressive 3.7cm/year. The Nazca also has an unusually flat subduction angle, causing it to have far ranging geographic effects (the Nazca plate affects parts of Bolivia's geography hundreds of miles east of the actual fault line). This subduction causes thrust faults, a type of reverse fault characterized by shallow the shallow angle of the relation to hanging wall and footwall of the fault.

The South American plate, being pushed up by the Nazca plate, has formed the impressive peaks of the Andes mountains; some peaks reach over 20,000 feet above sea level and the average peak height is 13,000 feet above sea level.

Mt Aconcagua south wall, Dimitri Mottl

The Andes are also a part of the Ring of Fire, a region of volcanoes around the of the Pacific Ocean. The Andes contains a large number of volcanoes, spread across multiple volcanic regions.

Along the Andes, faulting is predominant, but folding does occur in various regions as illustrated in the figure below, a photograph from the central Andes, in Peru.

Folded Permian carbonates, N.D Perez