If it can't be farmed, it's gotta be mined: We are stuck with the consequences of the Industrial Revolution. The really big one, the humanity's prodigious population, is something that society can't back away from without truly catastrophic dislocations. To maintain this population, we must maintian our industrial material culture. The mineral resources that make up the physical culture of modern human society come, to a large extent, from the ground. Thus, modern society depends, for better or worse, on knowledge of Geology.

Economic Geology: The geology of mineral resources, is truly the intersection of geosciences and economics. On a practical level, our geological attention is driven by economic conditions. In early 2008, the prices of some mineral resources, especially precious metals, were higher than in decades, sparking resurgent interest in mining operations. In spring of 2010, that interest has diminished only slightly.

Geologist and mine engineers don't just dig randomly. How do they know where to look?

First - some definitions: Note, this vocabulary is shared by geologists and practitioners of economics, "the dismal science."

To turn more strictly to the geological end of things, how does a material become concentrated above its crustal abundance?

Major mechanisms of mineral concentration:

  • Hydrothermal deposits: Hot water is transport medium.

  • Metamophic mineral deposits: Contact and regional metamorphism can concentrate valuable minerals. Examples include: Of course, metasomatism is also a means of concentrating minerals.

  • Magmatic (igneous) mineral deposits: Some igneous minerals are economically valuable. These form in three ways:

  • Sedimentary deposits: Economic minerals are concentrated in sedimentary rocks by four processes.

  • Residual mineral deposits: The percolation of groundwater, especially in the zone of leaching of laterite soils, can concentrate relatively insoluble minerals. We've already mentioned that laterites are rich in iron ore. They are also the source of bauxite, the common industrial source of aluminum.

    Energy Resources:

    Energy resources: A Fundamental fact - Human society is a manifestation of the Biosphere. Not surprisingly, we derive almost all of our energy from the Sun.

    Prior to the industrial era, all of the energy being harnassed by humans (muscle, wind, water power) had been beamed to Earth from the Sun very recently, at most within the few centuries. And that's where matters stood until the 18th century when steam power was harnassed to allow the industrial revolution:

    Fossil Fuel: For the first time, humans were making use of energy that was truly ancient - that had been beamed from the Sun millions to hundreds of millions of years earlier - "fossilized energy, if you will. Such energy sources are called Fossil Fuels.

    Since then, most innovations in energy production have involved finding different ways to turn turbines and push pistons harder and faster, and finding different things for those turbines to do. Thus, an electrical power station is steam turning a turbine turning an electrical dynamo. What makes that steam can be anything from a wood fire (rare these days) to the fission of heavy metals in a nuclear reactor.

    The paradox of fossil fuels: In the preindustrial era, energy was stored as carbohydrates in plant tissues which were built from atmospheric CO2 and H2O. Both are "greenhouse gasses." When plant tissue decomposes, is digested, or is burned, the gasses are restored to the atmosphere. What happens when the tissue is sequestered in the rock record?

    Coal: Metamorphosed remains of rapidly buried land plants.

    Alternatives to fossil fuels:

  • Solar: Complex chemical processes in photovoltaic cells produce electricity from sunlight. Useful on spacecraft where there are few alternatives. Passive-solar, in which careful building design reduces the need for heating and cooling may slightly alleviate our energy bill but is not, in itself, a source of energy. The use of photovoltaic cells to generate electricity brings about it's own set of issues:
  • Geothermal: In places with a steep geothermal gradient, water can be heated and used to turn a turbine by simply piping it into the ground and back out. Clean but very unevenly distributed geographically. Only countries with accessible regions of geothermal energy can use: