| 21. | The geologic history and origin of the northern plains are complex and still poorly understood.
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| 22. | Unlike many periods of geologic history the Jurassic did not end in a mass extinction.
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| 23. | The various kinds of " geologic history of events.
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| 24. | Another discovery was how youthful the ocean floor is in comparison to Earth's geologic history.
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| 25. | Recent global warming is one of many natural cycles of warming and cooling in geologic history.
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| 26. | The recognizable geologic history of the quadrangle ends with these events probably several billion years ago.
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| 27. | Sea level rose and fell often during this period of the Eocene Epoch in geologic history.
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| 28. | "A single rock outcrop can reveal the entire geologic history of this park, " he said.
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| 29. | The geologic history of Arctic Ocean basins is a major source of debate among marine geophysicists.
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| 30. | Much of the Plateau's landscape is related, in both appearance and geologic history, to the Grand Canyon.
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