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Paleozoic and Mesozoic Seas loading

During the Paleozoic and Mesozoic, six marine transgressions and regressions caused sea level to rise over the continents, leaving evidence in rocks in the Grand Canyon and elsewhere.
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Levels are CK-12's student achievement levels.
Basic Students matched to this level have a partial mastery of prerequisite knowledge and skills fundamental for proficient work.
At Grade (Proficient) Students matched to this level have demonstrated competency over challenging subject matter, including subject matter knowledge, application of such knowledge to real-world situations, and analytical skills appropriate to subject matter.
Advanced Students matched to this level are ready for material that requires superior performance and mastery.
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