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In section 1.7 of Geodynamics by D. Turcotte & G. Schubet it is stated that

"(...) continental crust cannot be destroyed by subduction"

which I cannot completely understand. So far I understand the oceanic lithosphere sinks at the trenches because it cools down and becomes denser (thermal contraction) as it moves away from the ocean ridges. So the logic is: buoyancy will make it descend.

But then again, isn't the continental crust thicker and denser? By the same logic above, it should sink as well.

Am I missing something? Thanks in advance for any comments

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    $\begingroup$ No, oceanic crust is denser than continental crust. This is why oceanic crust subducts continental one. $\endgroup$ – user18590 Jan 2 at 12:30
  • $\begingroup$ This question may help you understand it. $\endgroup$ – user18590 Jan 2 at 12:59
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    $\begingroup$ @Universal_learner Thanks for the reference! Very useful $\endgroup$ – caverac Jan 2 at 14:05
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It is continental crust which hs the greater buoyancy, so when it meets another plate of continental crust neither can subduct. Instead, they collide, crumple and fold, making them thicker and higher. An example of this is the collision between the Indo-Australian plate and the Eurasian plate, which has formed the Himalayas. Had the Indo-Australian plate been oceanic plate, which is thinner and less buoyant, it would have been subducted.

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