FIGURE 4.28 Air photo showing the San Andreas fault in Southern California. Note how the stream channel has been offset due to recent movement along this transform plate boundary.
Natural Resources
Earth naturally provides water and food needed for human survival, but it also provides mineral and energy resources that make modern societies possible. As pointed out in Chapter 1, water is absolutely essential for human bodies to function and also for the production of our crops (i.e., food), Plate tectonics then is tide to both our water and food supplies in part because it influences Earth’s climate and precipitation patterns as described above. In many dry regions of the world people depend almost entirely on rivers whose water comes from melting snow. This snow, in turn, accumulates in mountains that had been uplifted far above sea level by tectonic forces. For example, millions of people who depend on such meltwater live in the desert regions below the Himalayas of Asia, the Andes of South America, and the Rockies of North America. Plate tectonics also influences the formation and fertility of the soils in which we grow our crops.
In addition to water and food, modern societies depend on vast array of mineral and energy resources in order to supply the goods and services we enjoy. As you will learn in Chapters 12 and 13, mineral and energy deposits are not randomly located around the world, but rather form under very specific geologic conditions related to the rock cycle and plate tectonics. Consequently, some countries have the good fortune to be located in an area whose tectonic history has left them with valuable mineral and energy deposits. For example, Saudi Arabia is quite wealthy because of its enormous oil deposits, whereas many nearby African countries remain desperately poor in part due to a lack of mineral or energy resources.