Laboratory Manual for Introductory Geology 4e

EXERCISE 18.1
Humans and Earth System Cycles
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As we’ve seen, the extent to which human activity can alter geologic processes or change the duration of geologic cycles
varies widely. But not all reservoirs of the Earth System will be affected equally by human activity, or at the same rate.
(a) If there were no humans on the planet, which Earth System reservoir do you think would naturally experience the
most rapid or frequent changes over the next 50 years? Which do you think would experience the slowest pace of
change? Explain your reasoning.
(b) Bringing the human population back into the picture, which processes of the rock cycle, if any, do you think human
activity can affect? Explain how.
(c) Which processes of the tectonic cycle, if any, do you think human activity can affect? Explain.
(d) The duration of the hydrologic cycle depends on the reservoirs in which water is stored: water molecules remain
in the atmosphere for approximately 9 days, in rivers for about 2–6 months, in oceans for about 3,000 years, and in
deep groundwater for about 10,000 years, whereas ice remains in continental glaciers for hundreds of thousands
of years. Which of these time spans can be affected by human activity? Explain.
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474 CHAPTER 18 LOOKING TO THE FUTURE