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Why Do Mountains Stop Growing Even Though Tectonic Plates Keep Moving?
为什么山脉停止生长，尽管板块仍在持续运动？
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Mountains form when tectonic plates collide and push Earth's crust upward over millions of years.
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However, erosion by wind, water, and ice constantly wears them down at the same time.
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Gravity also limits how high mountains can become before rock layers begin to collapse sideways.
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Once uplift slows or stops, erosion gradually dominates and reduces their height over time.
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The Himalayas are still rising because India’s plate pushes northward faster than erosion removes material.
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But older ranges like the Appalachians have nearly stopped growing and now shrink slowly due to weathering.
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Rock strength, climate, and regional stress all affect whether a mountain range grows or declines.
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Scientists measure these changes using GPS satellites and laser elevation mapping over decades.
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Even active mountains reach equilibrium when uplift balances erosion — a key concept in geomorphology.
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This balance explains why Earth has no 20-kilometer-high peaks despite constant tectonic motion.