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Why are volcanoes common in some parts of the Andes?

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A car drives along the Trans-Canada Highway with Mount Sir Donald's sharp, snow-capped peak rising above forested slopes in the Selkirk Mountains, British Columbia. — mountain Mount Sir Donald in the Selkirk Mountains, British Columbia, looms above a segment of the Trans-Canada Highway.

Volcanoes are common in parts of the Andes because the mountain system is located along the Ring of Fire, a region characterized by intense tectonic activity.12

The primary driver of this volcanism is the subduction of the oceanic Nazca Plate beneath the continental [South American Plate]. As the Nazca Plate is forced downward into the mantle, the process triggers the intrusion of significant quantities of magma toward the surface. This volcanic activity has historically formed a nearly continuous chain of volcanoes along the western margin of South America, often referred to as the Cordillera Occidental.13

While the Andes are famous for these volcanoes, it is important to note that the range is not entirely volcanic; many of its highest peaks, such as Mount Aconcagua, were created primarily through crustal shortening and thickening rather than volcanic processes.3