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How does crustal shortening raise mountain belts?

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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.

Crustal shortening is a primary tectonic process that elevates mountain belts by thickening the Earth's crust. This occurs through two main mechanisms: the thrusting of one crustal block over another and the folding of rock layers.1

In settings such as Alpine- or Himalayan-type belts, the movement of one continent toward another leads to crustal shortening. Because continental crust is buoyant, it cannot be easily subducted into the asthenosphere. Instead, slices of crust are scraped off the descending plate and stacked onto the overriding continent. This process often involves ramp overthrusts, where slip along a fault lifts crystalline rocks from deep within the crust to the surface, creating high-relief mountain ranges.2

Additionally, the weight of these thrust slices flexes the intact continent downward, while sedimentary layers in front of the advancing range are compressed into anticlines and synclines. Ultimately, these mountains are supported by thick crustal roots, which buoy the range above the surrounding terrain in accordance with the principles of isostasy.234