"Geology is interesting as a pure science, and I believe that everyone can gain pleasure from learning about it. But there's more to geology than that, because rocks really are money. What I mean is that civilization rests on rocks:

• From iron to groundwater, from cut stone to road metal, society relies on a good supply of Earth products.
• The bigger the structure—bridge, landfill, power plant—the more we need to know about the ground to build it on.
• Everything we eat and drink and much of what we wear comes from soil, a thin biogeochemical layer of incredible complexity.
• Protection against geologic hazards, ranging from landslides to earthquakes, acid rain, volcanism, tsunamis and climate change, depends on our understanding of them."

Andrew Alden, http://geology.about.com