Besides magnetism, what major geological observation did Shen Kuo document regarding the Earth's structure?

Answer

Mountains that were currently inland had once been seabeds

Shen Kuo's geological observations included recognizing fossil evidence indicating that mountains that were currently inland had once been seabeds, supporting a theory of geological uplift and erosion.

Besides magnetism, what major geological observation did Shen Kuo document regarding the Earth's structure?
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