ENVIRONMENTAL ASPECTS OF THE GEOSPHERE
17.8 ENVIRONMENTAL ASPECTS OF THE GEOSPHERE
Most of the remainder of this chapter deals specifically with the environmental aspects of geology and human interactions with the geosphere. The following sections discuss how natural geological phenomena affect the environment through occurrences such as volcanic eruptions that might blast so much particulate matter and acid gas into the atmosphere that it could have a temporary effect on global climate, or massive earthquakes that disrupt surface topography and disturb the flow and distribution of groundwater and surface water. Also discussed are human influences on the geosphere and the strong connection between the geosphere and the anthrosphere.
Going back several billion years to its formation as a ball of dust particles collected from the universe and held together by gravitational forces, earth has witnessed constant environmental change and disruption. During its earlier eons, earth was a most inhospitable place for humans and, indeed, for any form of life. Heat generated by gravitational compression of primitive earth and by radioactive elements in its interior caused much of the mass of the planet to liquify. Relatively high-density iron sank into the core, and lighter minerals, primarily silicates, solidified and floated to the surface.
Although Earth changes almost imperceptibly during a human lifetime, the planet is in fact in a state of constant change and turmoil. It is known that continents have formed, broken apart, and moved around. Rock formations produced in ancient oceans have been thrust up onto continental land and huge masses of volcanic rock exist where volcanic activity is now unknown and has been absent for millions of years. Earth still unleashes enormous forces that push molten rock to the surface and move continents continuously as evidenced from volcanic activity, and from earth- quakes resulting from the movement of great land masses relative to each other. Earth’s surface is constantly changing as new mountain ranges are heaved up and old ones are worn down.
Humans have learned to work with, against, and around natural earth processes and phenomena to exploit earth’s resources and to make these processes and phe- nomena work for the benefit of humankind. Human efforts have been moderately successful in mitigating some of the major hazards posed by natural geospheric phe- nomena, although such endeavors often have had unforeseen detrimental conse- quences that sometimes are not manifested until many years after they were first applied. The survival of modern civilization and, indeed, of humankind will depend upon how intelligently humans work with the earth, rather than against it. That is why it is so important for humans to have a fundamental understanding of the geospheric environment.
An important consideration in human interaction with the geosphere is the application of engineering to geology. Engineering geology takes account of the geological characteristics of soil and rock in designing buildings, dams, highways, and other structures in a manner compatible with the geological strata on which they rest. Engineering geology must consider a large number of geological factors including type, strength, and fracture characteristics of rock, tendency for landslides to occur, susceptibility to settling, and likelihood of erosion. Engineering geology is an important consideration in land-use planning.