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