Relating to the study of crusts or crusty formations, whether on Earth's surface or in other contexts.
From crustology (a theoretical study of crusts) plus the suffix -ical meaning 'of or relating to.' It's an academic adjective form for crust-related studies.
Crustalogical research has shown that the Earth's crust is thinner under the oceans (about 6 kilometers) than under continents (about 30-40 kilometers), which is why oceanic crust is denser and heavier, causing ocean basins to sink.
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