Britannica
Sources used in this answer
- mountain - Alpine- (or Himalayan-)type belts
- mountain - Geomorphic characteristics
- continental landform - Orogenic geomorphic systems
- mountain - Mechanisms that support elevated terrains
- river - Valley evolution
- valley - Origin and evolution
- glacial landform - Erosional landforms of valley glaciers
- tectonic landform
Why do resistant rocks often form ridges in fold belts?
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mountain
Mount Sir Donald in the Selkirk Mountains, British Columbia,
looms
above
a segment of the Trans-Canada Highway.
In fold belts, the formation of ridges and valleys is primarily controlled by the varying resistance of rock layers to erosion.12
When sedimentary rock layers are folded into anticlines and synclines, the resulting landscape is subjected to erosional processes. Rocks that are more resistant to weathering and erosionāsuch as well-indurated sedimentary rocksāremain as elevated features, forming the ridges. Conversely, the valleys are carved into the weaker, less resistant rock layers.312
This differential erosion ensures that the topography of a fold belt is dominated by parallel ridges and valleys, a pattern clearly visible in regions like the Valley and Ridge province of the eastern United States.12