Outlook for fuel reserves
Long and detailed analysis of the complete fossil fuel cycle by Dr. M. K. Hubbert. Originally published in the McGraw-Hill Encylopedia of Energy ca. 1976.
See the Hubbert Tribute site, for a 22-page PDF of the entire article.
The beginning and ending paragraphs are posted here.
The significance of energy in human affairs can best be appreciated when it is realized that energy is involved in everything that happens on the Earth -- everything that moves.
The Earth is essentially a closed material system composed of the naturally occurring 92 chemical elements, all but a minute fraction of which are nonradioactive and hence obey the rules of conservation of matter and nontransmutability of the elements of classical chemistry.
Into and out of the Earth's surface environment there occurs a continuous influx, degradation, and efflux of energy in consequence of which the mobile materials of the Earth's surface undergo either continuous or intermittent circulation. In addition, there are certain large chemical, thermal, and nuclear stores of energy within minable or drillable depths beneath the Earth's surface.
...Fossil Fuels in Human History
The role of the fossil fuels in the longer span of human history can best be appreciated if one considers the period extending from 5000 years in the past to 5000 years in the future. On such a time scale the epoch of the fossil fuels is shown graphically in Fig. 19. This appears as a spike with a middle-80% width of about 3 centuries.
It is thus seen that the epoch of the exploitation of the fossil fuels is but an ephemeral event in the totality of human history. It is a unique event, nonetheless, in geological history.
Moreover, it is responsible for the world's present technological civilization and has exercised the most profound influence ever experienced by the human species during its entire biological existence.