Britannica
Sources used in this answer
How do crustal extension and thermal contraction reduce the height of mountain belts?
Created from Britannica articles
using AI.
AI can make mistakes, so verify using Britannica articles.
mountain
Mount Sir Donald in the Selkirk Mountains, British Columbia,
looms
above
a segment of the Trans-Canada Highway.
Beyond the primary role of erosion in wearing down elevated terrain, two specific tectonic processes contribute to the reduction of mountain belt heights:
- Horizontal crustal extension: This process involves the stretching and thinning of the Earth's crust. As the crust thins, the underlying crustal roots are reduced or eliminated, causing the mountain belt to widen while its mean elevation decreases.1
- Thermal contraction: As the outer part of the Earth cools, the associated thermal contraction leads to a reduction in the average height of the mountain belt.1
These processes act in opposition to the forces that build mountains, such as folding, faulting, and thermal expansion, which elevate terrain. Understanding these mechanisms is essential for analyzing how mountain belts evolve over time.23