Mass extinctionsa. are an example of 'uniformitarian' principles in geology b. are often triggered by magnetic field c. reversals occur at regularly spaced intervals in the geologic record d. denote a relatively sudden, global decrease in the diversity of life forms. e. are usually caused by a tsunami

If scientists only detect p waves in a certain layer of earths interior what does that tell us?

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Which of the following statements best describes what is occurring in the land surrounding the sahara desert? a desertification is increasing, and the desert is expanding. b. fewer people are trying to farm in this semiarid region. c. the desert is shrinking with the increased use of irrigation. d. increased urbanization has resulted in decreased deforestation. select the best answer from the choices provided mark this and return save and exit next submit