Explain the minimum depth needed for a feature to be considered a canyon?

422

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Explain what ways can igneous rock form two ways?

463

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Explain the difference between a canyon, gorge, and valley?

427

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Explain how old is the earth?

431

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Explain the mantle made of?

446

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Explain how continental heat flow is produced?

441

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Explain why does marble rarely contain fossils?

433

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