GEF

Unit 2  |  Humanity’s Ecological Footprint 43 production meant a boom in inventions and new products manufactured in large quantities. Factories and industrial cities grew as people moved to urban areas for work. The ability to produce and use energy became the cornerstone of develop- ment and economic growth. Near the end of the nineteenth century, an internal combus- tion engine was developed and with it the invention of the automobile. Oil began to overtake coal as the key fuel. Besides running machines, oil was used for a vast range of industrial applications, including the production of plastics, synthetic fibers, asphalt, and building materials. Modern coal-fired plants work much the same way as they did over a century ago, and 90 percent of electricity production in the U.S. comes from steam turbines— powered by coal, natural gas, or nuclear fission . Smog in an urban environment. INTERNAL COMBUSTION ENGINE An engine that generates heat and power through the combustion of a liquid fuel. NUCLEAR FISSION The process when an atom splits apart into smaller atoms, giving off a lot of energy. ?  DID YOU KNOW Air pollution in cities has been known to reach extreme levels. On one day in 1903, industrial pollution created smog in Los Angeles that was so thick some residents mistook the darkness for a solar eclipse.