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How are residual mountains formed by erosion?

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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.

Residual mountains are landforms that remain after long periods of erosion have worn down a region that was once a plateau or a broad, uplifted area.1

These mountains are typically characterized by their isolation, often standing apart from any discernible mountain chain. Their formation is a result of the differential wearing away of the Earth's surface; while surrounding areas are lowered by natural agencies such as water, wind, or ice, more resistant rock masses persist as elevated features.12

While many residual mountains exhibit low elevations due to the extensive history of erosion they have endured, their relief can vary from gentle to precipitous depending on the intensity of recent erosional processes. Notable examples of such features include Mount Katahdin in Maine, as well as entire ancient mountain chains like the Appalachian Mountains in North America and the Urals in Russia, which have persisted for hundreds of millions of years despite continuous denudation.1